Chi-Chun Tsai | University of Texas at Arlington (original) (raw)
Papers by Chi-Chun Tsai
Advanced Energy Materials, 2012
10 2 J SC and J D (mA/cm 2 ) Voltage (V) J SC J D Adv. Energy Mater. 2012,
ABSTRACT In the past, the crystallographic relationship between the gamma-phase and the alpha-pha... more ABSTRACT In the past, the crystallographic relationship between the gamma-phase and the alpha-phase in isotactic polypropylene was extensively studied via oligomers of iPP. We attempt to investigate how the crystal morphological changes take place in the gamma-phase using high molecular weight iPP-co-polyethylene samples. Due to the specific epitaxial growth of the gamma-phase on the elongated alpha-phase single crystals, two different morphologies were identified via transmission electron and atomic force microscopies. The first gamma-phase crystal morphology is needle-like. Selective area electron diffraction results showed that their [1 10] or [110] zone axis was parallel to the thin film normal. The growth of this type of epitaxial gamma-phase crystal was due to the stem direction in the initial alpha-phase single crystal being parallel to the thin film normal. The second gamma-phase crystal morphology was flat lamellae. This requires that the initial alpha-phase single crystal had to have a stem orientation tilted away from the thin film normal. Therefore, the sufficient and necessary condition for the gamma-phase morphological conversion from the needle-like crystal to the flat crystal is the change of the stem orientation direction of the initial alpha-phase single crystals.
The Journal of Physical Chemistry B, 2010
A novel organic− inorganic hybrid with two polyhedral oligosilsesquioxane (POSS) nanoparticles co... more A novel organic− inorganic hybrid with two polyhedral oligosilsesquioxane (POSS) nanoparticles covalently attached to perylene diimide (PDI) via a rigid 1, 4-phenylene linkage (POSS-PDI-POSS) was designed and synthesized to examine the effect of bulky ...
Soft Matter, 2012
ABSTRACT A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-t... more ABSTRACT A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamide (abbreviated as C22PhBAEO3) was designed and synthesized, and its phase behavior was fully investigated. The C22PhBAEO3 compound possesses a rigid core with three aromatic rings connected with amide bonds which possess the ability to form hydrogen (H) bonds. Three hydrophobic alkyl flexible tails and three hydrophilic flexible methyl terminated triethylene glycol tails are located at the other end. Major phase transitions and their origins in C22PhBAEO3 were studied via DSC and 1D WAXD techniques. Its hierarchical supramolecular crystal structure was further identified through combined techniques of 2D WAXD and SAXS as well as SAED. Results based on computer simulations confirmed the structure determination. It was found that the C22PhBAEO3 possesses three phases through various thermal treatments including a micro-phase separated columnar liquid crystal (col.) phase, a metastable crystal I phase and a stable crystal II phase. Among them, the crystal II phase showed that the columnar structure possesses 3D inter-column order and highly crystalline alkyl tails with a long-range overall orientational order. Four C22PhBAEO3 molecules self-assembled into a phase-separated disc with an ellipsoidal shape having a C2 symmetry along the disc normal. These discs then stacked on top of each other to generate a 1D asymmetric column through H-bonding, and further packed into a 3D long-range ordered monoclinic lattice. The unit cell parameters of this lattice were determined to be a = 5.08 nm, b = 2.41 nm, c = 0.98 nm, α = 90°, β = 90°, and γ = 70.5°. The alkyl chain tails crystallize within the hydrophobic layers and possess a relatively fixed orientation with respect to the column packing due to the selective interactions based on the hydrophobic/hydrophilic microphase separation. Both phase behaviour and unit cell structure showed significant difference compared with the symmetrically tapered counterparts. The results provided a new approach of fine-tuning not only in the Janus supramolecular structures but also in the formation pathway of the self-assembling process in order to meet the specific requirements for optical and biological applications.
Macromolecules, 2004
ABSTRACT The crystallization of the PLLA block within the microphase-separated lamellar microdoma... more ABSTRACT The crystallization of the PLLA block within the microphase-separated lamellar microdomain in a poly(styrene)-b-poly(l-lactide) (PS-PLLA) diblock copolymer was carried out from hard confinement (i.e., the crystallization temperature of PLLA (Tc,PLLA) < the glass transition temperature of PS (Tg,PS)) to soft confinement (i.e., Tc,PLLA ≥ Tg,PS), where interesting morphological evolution was observed. At Tc,PLLA < Tg,PS, a typical confined morphology was obtained, while at Tc,PLLA ≥ Tg,PS, a unique undulated morphology was seen for the first time. The amplitude and periodicity of the undulation instability are dependent upon the orientation of microphase-separated lamellae. The PLLA crystals under confinement formed perpendicular morphology having crystalline chains normal to the lamellae as evidenced by 2D small-angle X-ray scattering and wide-angle X-ray scattering. On the basis of morphological observations and crystallization kinetics studies, the undulation instability can be attributed to the change of crystallization mechanism from hard to soft confinement, which coincides with the transition from homogeneous to heterogeneous nucleation.
Journal of the American Chemical Society, 2004
Chirality-driven microphase-separated morphology, poly(l-lactide) (PLLA) left-handed nanohelices ... more Chirality-driven microphase-separated morphology, poly(l-lactide) (PLLA) left-handed nanohelices hexagonally packed in PS matrix, was obtained from chiral diblock copolymers, poly(styrene)-b-poly(l-lactide). This is perhaps for the first time; the helical superstructures of chiral block copolymers were generated in the bulk and self-assembled to a two-dimensionally (2D) packed lattice. Now, the analyses of block copolymer thermodynamics should be complicated by the chiral entities of constituted components. Orderly packed nanohelical channels can be obtained after hydrolysis, and this provides new opportunities for block copolymer applications in the fields of nanosciences.
Journal of Materials Chemistry, 2011
A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct ... more A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct symmetry ([60]fullerene (C 60 ) and polyhedral oligomeric silsesquioxane (POSS)) was synthesized and its solid state structures were characterized. The two types of nanoparticles are ...
The Journal of Chemical Physics, 2010
A series of inclusion complexes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(et... more A series of inclusion complexes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) with beta-cyclodextrin (beta-CD) was prepared. Their formation, structure, and dynamics were investigated by solution two-dimensional rotating-frame Overhauser effect spectroscopy (2D ROESY) and one-dimensional (1D) and 2D solid-state (13)C NMR. The inclusion complexes between the PEO-b-PPO-b-PEO copolymers and the beta-CDs were formed in aqueous solution and detected by 2D ROESY. The high efficiency of cross polarization and spin diffusion experiments in (13)C solid-state NMR showed that the mobility of the PPO blocks dramatically decreases after beta-CD complexation, indicating that they are selectively incorporated onto the PPO blocks. The hydrophobic cavities of beta-CD restrict the PPO block mobility, which is evidence of the formation of inclusion complexes in the solid state. The 2D wide-line separation NMR experiments suggested that beta-CDs only thread onto the PPO blocks while forming the inclusion complexes. The stoichiometry of inclusion complexes was studied using (1)H NMR, and a 3:1 (PO unit to beta-CD) was found for all inclusion complexes, which indicated that the number of threaded beta-CDs was only dependent on the molecular weight of the PPO blocks. 1D wide angle x-ray diffraction studies demonstrated that the beta-CD in the inclusion complex formed a channel-like structure that is different from the pure beta-CD crystal structure.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
Many injectable biomaterials have been produced as bulking agents for compression of urethral sph... more Many injectable biomaterials have been produced as bulking agents for compression of urethral sphincter or ureteral orifice for treating adult stress incontinence or vesicoureteral reflux in pediatrics. The agents being developed include glutaraldehyde crosslinked collagen, dextranomer/hyaluronic acid copolymer, pyrolytic carbon-coated zirconium oxide beads, polydimethyl-siloxane microparticles, polytetrafluoroethylene paste, autologous fats, autologous chondrocytes, and others. Though less invasive nature of these agents has gained their popularity as a quick solution of the disease symptoms, most of such treatments fail to produce good long-term efficacy. The failure is likely caused by the rapid degradation of material implants and the lack of tissue regeneration/integration properties. We thus believe that a good injectable biomaterial for incontinence should possess the following two properties: (1) to resist degradation and to reside in the implantation sites for a long period of time or (2) to enhance tissue regeneration and to establish permanent periurethral or subureteric tissue. Here we report some recent results for supporting this hypothesis.
Chemistry of Materials, 2010
Molecular orientation of a chemically linked rod-disk (cyanobiphenyl-triphenyl) liquid crystallin... more Molecular orientation of a chemically linked rod-disk (cyanobiphenyl-triphenyl) liquid crystalline (LC) molecule (RD12, where 12 is a number of carbon atoms in each alkyl chain linkage between the rod and the disk mesogens) in an antiparallel rubbed LC cell was investigated under vertically applied alternative current (AC) electric fields. Upon varying vertical AC electric fields from the initial state (0 V) to a fixed voltage ranging between 2.5 and 5.0 V, it was found that RD12 responded to the electric field with two-steps. The rod mesogen having a higher dipole interaction first aligned parallel to the electric field, while the disk mesogen behaved like an anchor of RD12. After the frustration and stabilization of rod mesogens, the in-plane axis of disk mesogen also aligned parallel to the electric field. Based on our experimental results, it was concluded that the peculiar molecular frustrations of RD12 under the vertical AC electric field occurred in a consequence of the competition among rods attached to both sides of the disk molecule. Furthermore, because molecular orientation of RD12 exhibiting a large birefringence is controlled by an electric field, RD12 can be used as a tunable optical switching material in the electro-optical devices.
ASAIO transactions / American Society for Artificial Internal Organs
A process was developed to coat complex medical devices with a thin, transparent, biocompatible f... more A process was developed to coat complex medical devices with a thin, transparent, biocompatible film. The film is based on silicone rubber (SR) but has higher albumin affinity than SR. Two polymer forms have been developed: one substitutes hydroxyl groups (OH), the other, 16 carbon acyl groups (C16) in the siloxane side chains. Oxymercuration/demercuration or hydroboration reactions can be used. SEM reveals film surfaces are smooth, uniform, and featureless. ATR/FTIR spectra and advancing/receding water contact angle measurements confirm the presence of surface OH groups and suggest the presence of surface acyl groups. Albumin adsorption and retention are markedly enhanced for surface OH and C16 concentrations as low as 5% reaction yield. Kinetics, isotherm, and competitive albumin/fibrinogen adsorption studies suggest that surface hydroxylation, and perhaps C16 acylation as well, markedly improve the albumin affinity, but not the fibrinogen affinity, of this material. The SR film c...
ASAIO transactions / American Society for Artificial Internal Organs
The authors have developed a method to increase the albumin affinity of silicone rubber-containin... more The authors have developed a method to increase the albumin affinity of silicone rubber-containing medical devices. A vinyl-methyl silicone co-monomer was hydroxylated via an oxymercuration-demercuration reaction and then film-coated on a silicone rubber sheet. C16 acylation of the -OH coated sheet was carried out by an esterification reaction catalyzed by 4-DMAP. FTIR spectroscopy confirmed the presence of -OH groups following the hydroxylation reaction, and (CH2)n groups following the acylation reaction. 125I-labeled albumin binding studies indicated graded enhancements, according to reagent concentration, with maximal 2.7X and 2.5X increases for 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. Incubation with a protein denaturant, sodium dodecyl sulfate (SDS), removed 73% of adsorbed albumin from unmodified controls, with only 25 and 34% removal from 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. These results suggest that -OH and C16 modified surf...
ASAIO transactions / American Society for Artificial Internal Organs
Hydroxylated and C16 acylated silicone rubber films were prepared with enhanced albumin binding. ... more Hydroxylated and C16 acylated silicone rubber films were prepared with enhanced albumin binding. Lee-White clotting times were significantly increased for both treatments. Hydroxylation significantly reduced C5a production. Hydroxylated silicone rubber femoral vein catheters in canines reduced 111In-labeled platelet activity, compared with bilateral silicone rubber catheter controls. The results suggest hydroxylated silicone rubber films have enhanced biocompatibility.
ASAIO Journal, 1993
The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) fi... more The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) films. An intermediate bifunctional coupling agent, polyvinylmethyl siloxane-comethyl-1-ethanol siloxane (PVMS-CO-MES), is prepared from a cyclic tetramer, vinyl-methyl siloxane, by an oxymercuration-demercuration reaction, and cross-linked to silicone rubber under mild peroxide catalytic conditions. Free mercury on the surface was obtained under many reaction conditions and is shown to materially enhance 125I-labeled albumin binding. The mechanism most likely occurs via disulfide bond breakage, protein denaturation, and aggregation. The possible role of iodine-mercury bonds, an artefactual source, is ruled out with the aid of total internal reflectance-fluorescence measurements of the albumin adsorption rate constant. Although in situ albumin aggregation via disulfide bond breakage is a potentially attractive method for biocompatible protein gel formation, the toxicity of mercury makes the current method unfit for clinical practice.
ASAIO Journal, 1993
An important element in the evaluation of biomaterials is quantification of the relationships and... more An important element in the evaluation of biomaterials is quantification of the relationships and the sequence of events between blood elements, blood flow, and the foreign surface. We adapted a qualitative two-dimensional 111In-labeled platelet imaging method to a quantitative noninvasive analysis of platelet uptake/release kinetics for infusion catheters in a canine model. Bilateral femoral vein 6 Fr. Groshong catheters (one treated with a hydroxylated siloxane to improve albumin affinity) were monitored at femoral vein sites with a GE 400T gamma camera, interfaced with a Technicare 560 image acquisition computer. The field of view was sufficiently large that all events below the diaphragm were recorded without having to move the camera. Image acquisition time was 2.5 min; images were obtained every 5-15 min for 3 hrs. Continuous recordings were obtained from bilateral ultrasonic velocity probes, attached distal to the catheter implant sites. A 5 ml blood sample was placed in the field to permit calibration of gamma emissions per pixel in terms of labeled platelet density. Signal compensation for near field capillary perfusion was performed. The two-dimensional platelet distribution was computed and displayed. Local, time dependent platelet accumulation on the catheters and adjacent vessel walls was observed. Platelet accumulation proceeded in irregular steps during the implant period. Loss of local platelet deposits was observed. Downstream reattachment of platelet emboli was inferred from simultaneous reductions and increases in local platelet densities at two catheter positions. Platelet attachment was inversely related to vein blood velocity.(ABSTRACT TRUNCATED AT 250 WORDS)
Biomaterials, 1995
Williams DF. Review. Tissue-biomaterial interactions. / Mater Sci 1987; 22: 3421-3445. Anderson J... more Williams DF. Review. Tissue-biomaterial interactions. / Mater Sci 1987; 22: 3421-3445. Anderson JM, Miller KM. Biomaterial biocompatibility and the macrophages. Biomaterials 1984; 5: 5-10. Sutherland K, Mahoney JR II, Coury A, Eaton JW. Degradation of biomaterials by phagocyte-derived oxidants. / Clin Invest 1993 (in press). Freyria AM, Chignier E, Guidollet J, Louisot P. Peritoneal macrophage response, an in viva model for the study of synthetic materials.
Advanced Energy Materials, 2012
10 2 J SC and J D (mA/cm 2 ) Voltage (V) J SC J D Adv. Energy Mater. 2012,
ABSTRACT In the past, the crystallographic relationship between the gamma-phase and the alpha-pha... more ABSTRACT In the past, the crystallographic relationship between the gamma-phase and the alpha-phase in isotactic polypropylene was extensively studied via oligomers of iPP. We attempt to investigate how the crystal morphological changes take place in the gamma-phase using high molecular weight iPP-co-polyethylene samples. Due to the specific epitaxial growth of the gamma-phase on the elongated alpha-phase single crystals, two different morphologies were identified via transmission electron and atomic force microscopies. The first gamma-phase crystal morphology is needle-like. Selective area electron diffraction results showed that their [1 10] or [110] zone axis was parallel to the thin film normal. The growth of this type of epitaxial gamma-phase crystal was due to the stem direction in the initial alpha-phase single crystal being parallel to the thin film normal. The second gamma-phase crystal morphology was flat lamellae. This requires that the initial alpha-phase single crystal had to have a stem orientation tilted away from the thin film normal. Therefore, the sufficient and necessary condition for the gamma-phase morphological conversion from the needle-like crystal to the flat crystal is the change of the stem orientation direction of the initial alpha-phase single crystals.
The Journal of Physical Chemistry B, 2010
A novel organic− inorganic hybrid with two polyhedral oligosilsesquioxane (POSS) nanoparticles co... more A novel organic− inorganic hybrid with two polyhedral oligosilsesquioxane (POSS) nanoparticles covalently attached to perylene diimide (PDI) via a rigid 1, 4-phenylene linkage (POSS-PDI-POSS) was designed and synthesized to examine the effect of bulky ...
Soft Matter, 2012
ABSTRACT A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-t... more ABSTRACT A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamide (abbreviated as C22PhBAEO3) was designed and synthesized, and its phase behavior was fully investigated. The C22PhBAEO3 compound possesses a rigid core with three aromatic rings connected with amide bonds which possess the ability to form hydrogen (H) bonds. Three hydrophobic alkyl flexible tails and three hydrophilic flexible methyl terminated triethylene glycol tails are located at the other end. Major phase transitions and their origins in C22PhBAEO3 were studied via DSC and 1D WAXD techniques. Its hierarchical supramolecular crystal structure was further identified through combined techniques of 2D WAXD and SAXS as well as SAED. Results based on computer simulations confirmed the structure determination. It was found that the C22PhBAEO3 possesses three phases through various thermal treatments including a micro-phase separated columnar liquid crystal (col.) phase, a metastable crystal I phase and a stable crystal II phase. Among them, the crystal II phase showed that the columnar structure possesses 3D inter-column order and highly crystalline alkyl tails with a long-range overall orientational order. Four C22PhBAEO3 molecules self-assembled into a phase-separated disc with an ellipsoidal shape having a C2 symmetry along the disc normal. These discs then stacked on top of each other to generate a 1D asymmetric column through H-bonding, and further packed into a 3D long-range ordered monoclinic lattice. The unit cell parameters of this lattice were determined to be a = 5.08 nm, b = 2.41 nm, c = 0.98 nm, α = 90°, β = 90°, and γ = 70.5°. The alkyl chain tails crystallize within the hydrophobic layers and possess a relatively fixed orientation with respect to the column packing due to the selective interactions based on the hydrophobic/hydrophilic microphase separation. Both phase behaviour and unit cell structure showed significant difference compared with the symmetrically tapered counterparts. The results provided a new approach of fine-tuning not only in the Janus supramolecular structures but also in the formation pathway of the self-assembling process in order to meet the specific requirements for optical and biological applications.
Macromolecules, 2004
ABSTRACT The crystallization of the PLLA block within the microphase-separated lamellar microdoma... more ABSTRACT The crystallization of the PLLA block within the microphase-separated lamellar microdomain in a poly(styrene)-b-poly(l-lactide) (PS-PLLA) diblock copolymer was carried out from hard confinement (i.e., the crystallization temperature of PLLA (Tc,PLLA) < the glass transition temperature of PS (Tg,PS)) to soft confinement (i.e., Tc,PLLA ≥ Tg,PS), where interesting morphological evolution was observed. At Tc,PLLA < Tg,PS, a typical confined morphology was obtained, while at Tc,PLLA ≥ Tg,PS, a unique undulated morphology was seen for the first time. The amplitude and periodicity of the undulation instability are dependent upon the orientation of microphase-separated lamellae. The PLLA crystals under confinement formed perpendicular morphology having crystalline chains normal to the lamellae as evidenced by 2D small-angle X-ray scattering and wide-angle X-ray scattering. On the basis of morphological observations and crystallization kinetics studies, the undulation instability can be attributed to the change of crystallization mechanism from hard to soft confinement, which coincides with the transition from homogeneous to heterogeneous nucleation.
Journal of the American Chemical Society, 2004
Chirality-driven microphase-separated morphology, poly(l-lactide) (PLLA) left-handed nanohelices ... more Chirality-driven microphase-separated morphology, poly(l-lactide) (PLLA) left-handed nanohelices hexagonally packed in PS matrix, was obtained from chiral diblock copolymers, poly(styrene)-b-poly(l-lactide). This is perhaps for the first time; the helical superstructures of chiral block copolymers were generated in the bulk and self-assembled to a two-dimensionally (2D) packed lattice. Now, the analyses of block copolymer thermodynamics should be complicated by the chiral entities of constituted components. Orderly packed nanohelical channels can be obtained after hydrolysis, and this provides new opportunities for block copolymer applications in the fields of nanosciences.
Journal of Materials Chemistry, 2011
A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct ... more A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct symmetry ([60]fullerene (C 60 ) and polyhedral oligomeric silsesquioxane (POSS)) was synthesized and its solid state structures were characterized. The two types of nanoparticles are ...
The Journal of Chemical Physics, 2010
A series of inclusion complexes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(et... more A series of inclusion complexes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) with beta-cyclodextrin (beta-CD) was prepared. Their formation, structure, and dynamics were investigated by solution two-dimensional rotating-frame Overhauser effect spectroscopy (2D ROESY) and one-dimensional (1D) and 2D solid-state (13)C NMR. The inclusion complexes between the PEO-b-PPO-b-PEO copolymers and the beta-CDs were formed in aqueous solution and detected by 2D ROESY. The high efficiency of cross polarization and spin diffusion experiments in (13)C solid-state NMR showed that the mobility of the PPO blocks dramatically decreases after beta-CD complexation, indicating that they are selectively incorporated onto the PPO blocks. The hydrophobic cavities of beta-CD restrict the PPO block mobility, which is evidence of the formation of inclusion complexes in the solid state. The 2D wide-line separation NMR experiments suggested that beta-CDs only thread onto the PPO blocks while forming the inclusion complexes. The stoichiometry of inclusion complexes was studied using (1)H NMR, and a 3:1 (PO unit to beta-CD) was found for all inclusion complexes, which indicated that the number of threaded beta-CDs was only dependent on the molecular weight of the PPO blocks. 1D wide angle x-ray diffraction studies demonstrated that the beta-CD in the inclusion complex formed a channel-like structure that is different from the pure beta-CD crystal structure.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
Many injectable biomaterials have been produced as bulking agents for compression of urethral sph... more Many injectable biomaterials have been produced as bulking agents for compression of urethral sphincter or ureteral orifice for treating adult stress incontinence or vesicoureteral reflux in pediatrics. The agents being developed include glutaraldehyde crosslinked collagen, dextranomer/hyaluronic acid copolymer, pyrolytic carbon-coated zirconium oxide beads, polydimethyl-siloxane microparticles, polytetrafluoroethylene paste, autologous fats, autologous chondrocytes, and others. Though less invasive nature of these agents has gained their popularity as a quick solution of the disease symptoms, most of such treatments fail to produce good long-term efficacy. The failure is likely caused by the rapid degradation of material implants and the lack of tissue regeneration/integration properties. We thus believe that a good injectable biomaterial for incontinence should possess the following two properties: (1) to resist degradation and to reside in the implantation sites for a long period of time or (2) to enhance tissue regeneration and to establish permanent periurethral or subureteric tissue. Here we report some recent results for supporting this hypothesis.
Chemistry of Materials, 2010
Molecular orientation of a chemically linked rod-disk (cyanobiphenyl-triphenyl) liquid crystallin... more Molecular orientation of a chemically linked rod-disk (cyanobiphenyl-triphenyl) liquid crystalline (LC) molecule (RD12, where 12 is a number of carbon atoms in each alkyl chain linkage between the rod and the disk mesogens) in an antiparallel rubbed LC cell was investigated under vertically applied alternative current (AC) electric fields. Upon varying vertical AC electric fields from the initial state (0 V) to a fixed voltage ranging between 2.5 and 5.0 V, it was found that RD12 responded to the electric field with two-steps. The rod mesogen having a higher dipole interaction first aligned parallel to the electric field, while the disk mesogen behaved like an anchor of RD12. After the frustration and stabilization of rod mesogens, the in-plane axis of disk mesogen also aligned parallel to the electric field. Based on our experimental results, it was concluded that the peculiar molecular frustrations of RD12 under the vertical AC electric field occurred in a consequence of the competition among rods attached to both sides of the disk molecule. Furthermore, because molecular orientation of RD12 exhibiting a large birefringence is controlled by an electric field, RD12 can be used as a tunable optical switching material in the electro-optical devices.
ASAIO transactions / American Society for Artificial Internal Organs
A process was developed to coat complex medical devices with a thin, transparent, biocompatible f... more A process was developed to coat complex medical devices with a thin, transparent, biocompatible film. The film is based on silicone rubber (SR) but has higher albumin affinity than SR. Two polymer forms have been developed: one substitutes hydroxyl groups (OH), the other, 16 carbon acyl groups (C16) in the siloxane side chains. Oxymercuration/demercuration or hydroboration reactions can be used. SEM reveals film surfaces are smooth, uniform, and featureless. ATR/FTIR spectra and advancing/receding water contact angle measurements confirm the presence of surface OH groups and suggest the presence of surface acyl groups. Albumin adsorption and retention are markedly enhanced for surface OH and C16 concentrations as low as 5% reaction yield. Kinetics, isotherm, and competitive albumin/fibrinogen adsorption studies suggest that surface hydroxylation, and perhaps C16 acylation as well, markedly improve the albumin affinity, but not the fibrinogen affinity, of this material. The SR film c...
ASAIO transactions / American Society for Artificial Internal Organs
The authors have developed a method to increase the albumin affinity of silicone rubber-containin... more The authors have developed a method to increase the albumin affinity of silicone rubber-containing medical devices. A vinyl-methyl silicone co-monomer was hydroxylated via an oxymercuration-demercuration reaction and then film-coated on a silicone rubber sheet. C16 acylation of the -OH coated sheet was carried out by an esterification reaction catalyzed by 4-DMAP. FTIR spectroscopy confirmed the presence of -OH groups following the hydroxylation reaction, and (CH2)n groups following the acylation reaction. 125I-labeled albumin binding studies indicated graded enhancements, according to reagent concentration, with maximal 2.7X and 2.5X increases for 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. Incubation with a protein denaturant, sodium dodecyl sulfate (SDS), removed 73% of adsorbed albumin from unmodified controls, with only 25 and 34% removal from 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. These results suggest that -OH and C16 modified surf...
ASAIO transactions / American Society for Artificial Internal Organs
Hydroxylated and C16 acylated silicone rubber films were prepared with enhanced albumin binding. ... more Hydroxylated and C16 acylated silicone rubber films were prepared with enhanced albumin binding. Lee-White clotting times were significantly increased for both treatments. Hydroxylation significantly reduced C5a production. Hydroxylated silicone rubber femoral vein catheters in canines reduced 111In-labeled platelet activity, compared with bilateral silicone rubber catheter controls. The results suggest hydroxylated silicone rubber films have enhanced biocompatibility.
ASAIO Journal, 1993
The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) fi... more The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) films. An intermediate bifunctional coupling agent, polyvinylmethyl siloxane-comethyl-1-ethanol siloxane (PVMS-CO-MES), is prepared from a cyclic tetramer, vinyl-methyl siloxane, by an oxymercuration-demercuration reaction, and cross-linked to silicone rubber under mild peroxide catalytic conditions. Free mercury on the surface was obtained under many reaction conditions and is shown to materially enhance 125I-labeled albumin binding. The mechanism most likely occurs via disulfide bond breakage, protein denaturation, and aggregation. The possible role of iodine-mercury bonds, an artefactual source, is ruled out with the aid of total internal reflectance-fluorescence measurements of the albumin adsorption rate constant. Although in situ albumin aggregation via disulfide bond breakage is a potentially attractive method for biocompatible protein gel formation, the toxicity of mercury makes the current method unfit for clinical practice.
ASAIO Journal, 1993
An important element in the evaluation of biomaterials is quantification of the relationships and... more An important element in the evaluation of biomaterials is quantification of the relationships and the sequence of events between blood elements, blood flow, and the foreign surface. We adapted a qualitative two-dimensional 111In-labeled platelet imaging method to a quantitative noninvasive analysis of platelet uptake/release kinetics for infusion catheters in a canine model. Bilateral femoral vein 6 Fr. Groshong catheters (one treated with a hydroxylated siloxane to improve albumin affinity) were monitored at femoral vein sites with a GE 400T gamma camera, interfaced with a Technicare 560 image acquisition computer. The field of view was sufficiently large that all events below the diaphragm were recorded without having to move the camera. Image acquisition time was 2.5 min; images were obtained every 5-15 min for 3 hrs. Continuous recordings were obtained from bilateral ultrasonic velocity probes, attached distal to the catheter implant sites. A 5 ml blood sample was placed in the field to permit calibration of gamma emissions per pixel in terms of labeled platelet density. Signal compensation for near field capillary perfusion was performed. The two-dimensional platelet distribution was computed and displayed. Local, time dependent platelet accumulation on the catheters and adjacent vessel walls was observed. Platelet accumulation proceeded in irregular steps during the implant period. Loss of local platelet deposits was observed. Downstream reattachment of platelet emboli was inferred from simultaneous reductions and increases in local platelet densities at two catheter positions. Platelet attachment was inversely related to vein blood velocity.(ABSTRACT TRUNCATED AT 250 WORDS)
Biomaterials, 1995
Williams DF. Review. Tissue-biomaterial interactions. / Mater Sci 1987; 22: 3421-3445. Anderson J... more Williams DF. Review. Tissue-biomaterial interactions. / Mater Sci 1987; 22: 3421-3445. Anderson JM, Miller KM. Biomaterial biocompatibility and the macrophages. Biomaterials 1984; 5: 5-10. Sutherland K, Mahoney JR II, Coury A, Eaton JW. Degradation of biomaterials by phagocyte-derived oxidants. / Clin Invest 1993 (in press). Freyria AM, Chignier E, Guidollet J, Louisot P. Peritoneal macrophage response, an in viva model for the study of synthetic materials.