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Papers by Tomasz Kazmierczak

Optics Express, 2008

The design, fabrication, and properties of one of a new class of gradient-index lenses are report... more The design, fabrication, and properties of one of a new class of gradient-index lenses are reported. The lens is an f/2.25 GRIN singlet based on a nanolayered polymer composite material, designed to correct for spherical aberration. The light gathering and focusing properties of the polymer lens are compared to a homogeneous BK7 glass singlet with a similar f-number. The modulation transfer function of the polymer GRIN lens exceeded that of the homogeneous glass lens at all spatial frequencies and was as much as 3 times better at 5 cyc/mm. The weight of the polymer lens was approximately an order of magnitude less than the homogeneous glass lens.

We have fabricated all-polymer lasers both as distributed feedback lasers (DFB) and distributed B... more We have fabricated all-polymer lasers both as distributed feedback lasers (DFB) and distributed Bragg reflector (DBR) lasers. For the DBR lasers, a layer of polymer doped with the laser dye is laminated between two multilayer polymer mirrors. The mirrors were made using the co-extrusion process combining PMMA alternated with polystyrene with 128 layers for each mirror. Two dyes were employed,

Macromolecular Rapid Communications, 2007

Polymer, 2010

Morphology of undeformed polyethylene crystals obtained by high pressure crystallization was inve... more Morphology of undeformed polyethylene crystals obtained by high pressure crystallization was investigated by SEM. It was revealed by exposing the interior of the samples by microtoming followed by permanganic etching. The etching procedure was refined to reveal defected sites of lamellae in addition to differentiation of crystalline and amorphous phases. From 1 to 3 screw dislocations with large Burgers vector per 1 mm 2 of lamellae basal planes were detected. Lamellae, when viewed edge-on give an impression of a "blocky architecture", while their real shape, as seen on SEM images of flat-on and oblique lamellae, resembles platelets with a few defects in the form of screw dislocations protruding a platelet. High pressure-crystallized polyethylene samples were deformed plastically by uniaxial compression and were studied by SEM and AFM. When the deformation is interrupted dislocations are arrested within the crystals. It was observed that in contrast to undeformed samples, the side faces of deformed lamellae were not any longer smooth and a large number of screw dislocations with low Burgers vectors crossing the lamellae thickness could be distinguished. These observations are in accordance with polymer crystal plasticity theory that relies on the rate controlled nucleation and propagation of screw dislocations across polymer crystals. An existence of numerous screw dislocations arrested in lamellae is a direct proof of action of fine crystallographic slips along the macromolecular chains in PE crystals during plastic deformation. The kinking of lamellae due to plastic deformation was also observed. Large sections of lamellae between kinks rotated towards the plane of compression while the chain stems in lamellae rotated in the opposite direction, away from the compression direction, which is a signature of the fine crystallographic slip. Plastically deformed polyethylene crystals are highly defected due to many dislocations incorporated within them e the density of dislocations was approximated as 10 16 m À2. However, deformed crystal melting temperature is nearly unaffected while the heat of melting is slightly reduced, yet only in thin crystals. It suggests that the arrested dislocations contribute more to the surface energy of lamellae basal planes rather than to a bulk energy of polyethylene crystals.

Optics and Photonics News, 2008

Polymer, 2005

ABSTRACT Based on our experiments on polyethylene where we have observed a constant level of plas... more ABSTRACT Based on our experiments on polyethylene where we have observed a constant level of plastic resistance, independent of lamella thickness exceeding 40 nm, we have fundamentally re-considered the rate controlling mechanisms of crystal plasticity in semi-crystalline polymers. In this we have not only re-examined and made modifications to the widely accepted mechanism of Young (Young RJ. Mater Forum 1988;11:210.) of monolithic nucleation of screw dislocations from edges of crystalline lamellae predicting an increase in plastic resistance with increasing lamella thickness, but we are proposing here two new modes of nucleation of both edge and screw dislocation half loops from lamella faces that are independent of lamella thickness. These two new modes of dislocation nucleation explain well the observed transition from a plastic resistance increasing with lamella thickness to one of constant resistance above a lamella thickness of ca. 35 nm in polyethylene. They also provide a more satisfactory framework to explain the temperature and strain rate dependence of the plastic resistance of polyethylene and predict the observed levels of activation volumes determined by us.

Polymer, 2005

ABSTRACT Plastic deformation of polyethylene (PE) samples with crystals of various thickness was ... more ABSTRACT Plastic deformation of polyethylene (PE) samples with crystals of various thickness was studied during uniaxial compression with initial compressive strain rates of 5.5×10−5, 1.1×10−3 and 5.5×10−3 s−1. Samples with a broad range of crystals thickness, from usual 20 up to 170 nm, were obtained by crystallization under high pressure. The samples underwent recoverable compression below the compression ratio of 1.05–1.07. Following yield, plastic flow sets in above a compression ratio of 1.12. At a compression rate of 5.5×10−5 s−1 the yield stress increases with the increase of crystal thickness up to 40 nm. For crystals thicker than 40 nm the yield stress levels off and remains constant. This experimental dependence was compared with the model developed on the basis of classical crystal plasticity and the monolithic nucleation of screw dislocations from polymer crystals. In that model contrary to the experimental evidence, the yield stress does not saturate with increase of crystal thickness. The activation volumes determined from strain rate jump experiments and from stress relaxation for crystals thicker than 40 nm are nearly constant at a level of 8.1 nm3. This activation length agrees very well with 40 nm for crystal thickness above which the yield stress levels off. It is proposed, as shown in a companion communication, that for PE crystals thicker than 40 nm two other modes of dislocation emission in the form of half loops of edge and screw dislocations begin to govern the strain rate, which no longer depend on lamella thickness.

Optics Express, 2008

A new type of solid-state variable focal length lens is described. It is based on shape changes i... more A new type of solid-state variable focal length lens is described. It is based on shape changes in an elastomeric membrane driven by compression of a reservoir of a polymer gel. A novel fabrication process based on individual lens components allows for customization of lens power based on the desired application. The lens shape as a function of applied compressive strain is measured using direct surface profile measurements. The focal length of a solid state lens was reversibly changed by a factor of 1.9. Calculated back focal lengths of the lens were consistent with experimental measurements.

Optics Express, 2008

We have assembled and studied melt-processed all-polymer lasers comprising distributed Bragg refl... more We have assembled and studied melt-processed all-polymer lasers comprising distributed Bragg reflectors that were fabricated in large sheets using a co-extrusion process and define the cavities for dye-doped compression-molded polymer gain core sheets. Distributed Bragg reflector (DBR) resonators consisting of 128 alternating poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) layers were produced by multilayer coextrusion. Gain media were fabricated by compression-molding thermoplastic host polymers doped with organic laser dyes. Both processing methods can be used in high-throughput roll-to-roll manufacturing. Optically pumped DBR lasers assembled from these components display single and multimode lasing in the reflection band of the resonators, with a slope efficiency of nearly 19% and lasing thresholds as low as 90μJ/cm 2. The lasing wavelength can be controlled via the layer thickness of the DBR resonator films, and variation of the laser dye. Studies of threshold and efficiency are in agreement with models for endpumped lasers.

Materials Science and Engineering: A, 2001

It is often observed that the plastic deformation of crystalline polymers, especially on drawing,... more It is often observed that the plastic deformation of crystalline polymers, especially on drawing, causes significant amount of cavitation. Cavitation can be suppressed in the process of rolling due to compressive component. An innovative method of obtaining highly oriented polymeric materials is by unidirectional rolling in a channel formed on the circumference of one roll with another roll, having the

Journal of Applied Polymer Science, 2009

A stretching process to enhance the stiffness of an elastomeric propylene-ethylene copolymer thro... more A stretching process to enhance the stiffness of an elastomeric propylene-ethylene copolymer through orientation was examined. The tensile extension was performed at various temperatures within the unusually broad melting range of the copolymer. Stretching transformed the unmelted lamellar crystals into shishkebab fibers that acted as a scaffold for an elastomeric matrix of entangled, amorphous chains. Density measurements indicated that the process did not significantly affect the amount of crystallinity, which was about 23%. If the specimen was recrystallized by cooling after it recovered from the stretched state, the amount of orientation decreased with increasing stretching temperature. However , if recrystallization occurred in the stretched state, it led to the formation of a second crystalline network that prevented contraction of the oriented crystalline structure during strain recovery. It was suggested that the second network was anchored by a 0-PP daughter lamellae that crystallized epitaxially on the a-PP mother crystals of the extended fibrils. Although the manner in which the films were stretched and recrystallized strongly affected the modulus, good elasticity of the stretched films revealed the persistence of an elastomeric network. V

Journal of Applied Polymer Science, 2003

ABSTRACT The orientation of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films with differe... more ABSTRACT The orientation of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films with different morphologies were studied by wide-angle X-ray diffraction. Different structures were obtained by thermally treating biaxially stretched PEN samples. Virgin and thermally treated (1 h at 240, 250, and 260°C) samples of PEN bioriented films were characterized by DSC to determine the glass-transition temperature and the crystallinity ratio. To define the orientation of crystallites in the 25 μm thick bioriented samples, pole figures were recorded for various PEN samples, as a function of their position in the transverse drawing direction. The significant result is that there is a dominant crystal population, whose c-axis direction varies from +45° at one sample edge to −45° at the other edge, the orientation at the center being parallel to the transverse direction. There is also a secondary population, which can be seen only near the center. DSC studies also showed that by increasing the annealing temperature the crystallinity ratio was increased and pole figures showed that the texture was modified, probably because of disorientation mainly from an annealing temperature of 260°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2224–2232, 2003

Journal of Applied Polymer Science, 2002

We investigated the possibility of obtaining high-density polyethylene (PE) samples with crystals... more We investigated the possibility of obtaining high-density polyethylene (PE) samples with crystals in a broad range of thicknesses. PE samples solidified by slow cooling were subjected to hydrostatic pressure at room temperature and then heated to the region of mobile pseudohexagonal form, without being passed through melting. The chains were allowed to rearrange for a period of time to a more extended chain conformation, forming larger crystals. During cooling under pressure, the transformation to orthorhombic crystals of larger thickness occurred. The thickness of the crystals was then controlled by pressure, temperature, and annealing time at high temperatures. The temperature and the pressure in the high-pressure cell was maintained at constant level within 230-295°C and 260-630 MPa, respectively. In this way, we transformed under pressure chain-folded PE crystals to partly chain-extended crystals with peak melting temperatures up to 144.85°C. A range of samples with crystals 20-160 nm thick were produced and characterized with several techniques, including wideand small-angle X-ray scattering, conventional and temperature-modulated differential scanning calorimetry, dynamic mechanical analysis, and scanning electron, atomic force, and light microscopy as well as low-frequency Raman spectroscopy. Changes in crystallographic unit cell dimensions were observed for crystals with different thicknesses. Crystallinity degree increased with increases in the lamellar thickness up to some level. The initial spherulitic structure deteriorated due to a multifold increase in the lamellar thickness. Oriented samples subjected to annealing in the pseudohexagonal region did not lose the crystal orientation while crystals grew thicker and the crystallinity degree increased; however, no drastic change to noncrystalline phase topology and structure was noticed.

Macromolecular Symposia, 2000

Optics Express, 2008

The design, fabrication, and properties of one of a new class of gradient-index lenses are report... more The design, fabrication, and properties of one of a new class of gradient-index lenses are reported. The lens is an f/2.25 GRIN singlet based on a nanolayered polymer composite material, designed to correct for spherical aberration. The light gathering and focusing properties of the polymer lens are compared to a homogeneous BK7 glass singlet with a similar f-number. The modulation transfer function of the polymer GRIN lens exceeded that of the homogeneous glass lens at all spatial frequencies and was as much as 3 times better at 5 cyc/mm. The weight of the polymer lens was approximately an order of magnitude less than the homogeneous glass lens.

We have fabricated all-polymer lasers both as distributed feedback lasers (DFB) and distributed B... more We have fabricated all-polymer lasers both as distributed feedback lasers (DFB) and distributed Bragg reflector (DBR) lasers. For the DBR lasers, a layer of polymer doped with the laser dye is laminated between two multilayer polymer mirrors. The mirrors were made using the co-extrusion process combining PMMA alternated with polystyrene with 128 layers for each mirror. Two dyes were employed,

Macromolecular Rapid Communications, 2007

Polymer, 2010

Morphology of undeformed polyethylene crystals obtained by high pressure crystallization was inve... more Morphology of undeformed polyethylene crystals obtained by high pressure crystallization was investigated by SEM. It was revealed by exposing the interior of the samples by microtoming followed by permanganic etching. The etching procedure was refined to reveal defected sites of lamellae in addition to differentiation of crystalline and amorphous phases. From 1 to 3 screw dislocations with large Burgers vector per 1 mm 2 of lamellae basal planes were detected. Lamellae, when viewed edge-on give an impression of a "blocky architecture", while their real shape, as seen on SEM images of flat-on and oblique lamellae, resembles platelets with a few defects in the form of screw dislocations protruding a platelet. High pressure-crystallized polyethylene samples were deformed plastically by uniaxial compression and were studied by SEM and AFM. When the deformation is interrupted dislocations are arrested within the crystals. It was observed that in contrast to undeformed samples, the side faces of deformed lamellae were not any longer smooth and a large number of screw dislocations with low Burgers vectors crossing the lamellae thickness could be distinguished. These observations are in accordance with polymer crystal plasticity theory that relies on the rate controlled nucleation and propagation of screw dislocations across polymer crystals. An existence of numerous screw dislocations arrested in lamellae is a direct proof of action of fine crystallographic slips along the macromolecular chains in PE crystals during plastic deformation. The kinking of lamellae due to plastic deformation was also observed. Large sections of lamellae between kinks rotated towards the plane of compression while the chain stems in lamellae rotated in the opposite direction, away from the compression direction, which is a signature of the fine crystallographic slip. Plastically deformed polyethylene crystals are highly defected due to many dislocations incorporated within them e the density of dislocations was approximated as 10 16 m À2. However, deformed crystal melting temperature is nearly unaffected while the heat of melting is slightly reduced, yet only in thin crystals. It suggests that the arrested dislocations contribute more to the surface energy of lamellae basal planes rather than to a bulk energy of polyethylene crystals.

Optics and Photonics News, 2008

Polymer, 2005

ABSTRACT Based on our experiments on polyethylene where we have observed a constant level of plas... more ABSTRACT Based on our experiments on polyethylene where we have observed a constant level of plastic resistance, independent of lamella thickness exceeding 40 nm, we have fundamentally re-considered the rate controlling mechanisms of crystal plasticity in semi-crystalline polymers. In this we have not only re-examined and made modifications to the widely accepted mechanism of Young (Young RJ. Mater Forum 1988;11:210.) of monolithic nucleation of screw dislocations from edges of crystalline lamellae predicting an increase in plastic resistance with increasing lamella thickness, but we are proposing here two new modes of nucleation of both edge and screw dislocation half loops from lamella faces that are independent of lamella thickness. These two new modes of dislocation nucleation explain well the observed transition from a plastic resistance increasing with lamella thickness to one of constant resistance above a lamella thickness of ca. 35 nm in polyethylene. They also provide a more satisfactory framework to explain the temperature and strain rate dependence of the plastic resistance of polyethylene and predict the observed levels of activation volumes determined by us.

Polymer, 2005

ABSTRACT Plastic deformation of polyethylene (PE) samples with crystals of various thickness was ... more ABSTRACT Plastic deformation of polyethylene (PE) samples with crystals of various thickness was studied during uniaxial compression with initial compressive strain rates of 5.5×10−5, 1.1×10−3 and 5.5×10−3 s−1. Samples with a broad range of crystals thickness, from usual 20 up to 170 nm, were obtained by crystallization under high pressure. The samples underwent recoverable compression below the compression ratio of 1.05–1.07. Following yield, plastic flow sets in above a compression ratio of 1.12. At a compression rate of 5.5×10−5 s−1 the yield stress increases with the increase of crystal thickness up to 40 nm. For crystals thicker than 40 nm the yield stress levels off and remains constant. This experimental dependence was compared with the model developed on the basis of classical crystal plasticity and the monolithic nucleation of screw dislocations from polymer crystals. In that model contrary to the experimental evidence, the yield stress does not saturate with increase of crystal thickness. The activation volumes determined from strain rate jump experiments and from stress relaxation for crystals thicker than 40 nm are nearly constant at a level of 8.1 nm3. This activation length agrees very well with 40 nm for crystal thickness above which the yield stress levels off. It is proposed, as shown in a companion communication, that for PE crystals thicker than 40 nm two other modes of dislocation emission in the form of half loops of edge and screw dislocations begin to govern the strain rate, which no longer depend on lamella thickness.

Optics Express, 2008

A new type of solid-state variable focal length lens is described. It is based on shape changes i... more A new type of solid-state variable focal length lens is described. It is based on shape changes in an elastomeric membrane driven by compression of a reservoir of a polymer gel. A novel fabrication process based on individual lens components allows for customization of lens power based on the desired application. The lens shape as a function of applied compressive strain is measured using direct surface profile measurements. The focal length of a solid state lens was reversibly changed by a factor of 1.9. Calculated back focal lengths of the lens were consistent with experimental measurements.

Optics Express, 2008

We have assembled and studied melt-processed all-polymer lasers comprising distributed Bragg refl... more We have assembled and studied melt-processed all-polymer lasers comprising distributed Bragg reflectors that were fabricated in large sheets using a co-extrusion process and define the cavities for dye-doped compression-molded polymer gain core sheets. Distributed Bragg reflector (DBR) resonators consisting of 128 alternating poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) layers were produced by multilayer coextrusion. Gain media were fabricated by compression-molding thermoplastic host polymers doped with organic laser dyes. Both processing methods can be used in high-throughput roll-to-roll manufacturing. Optically pumped DBR lasers assembled from these components display single and multimode lasing in the reflection band of the resonators, with a slope efficiency of nearly 19% and lasing thresholds as low as 90μJ/cm 2. The lasing wavelength can be controlled via the layer thickness of the DBR resonator films, and variation of the laser dye. Studies of threshold and efficiency are in agreement with models for endpumped lasers.

Materials Science and Engineering: A, 2001

It is often observed that the plastic deformation of crystalline polymers, especially on drawing,... more It is often observed that the plastic deformation of crystalline polymers, especially on drawing, causes significant amount of cavitation. Cavitation can be suppressed in the process of rolling due to compressive component. An innovative method of obtaining highly oriented polymeric materials is by unidirectional rolling in a channel formed on the circumference of one roll with another roll, having the

Journal of Applied Polymer Science, 2009

A stretching process to enhance the stiffness of an elastomeric propylene-ethylene copolymer thro... more A stretching process to enhance the stiffness of an elastomeric propylene-ethylene copolymer through orientation was examined. The tensile extension was performed at various temperatures within the unusually broad melting range of the copolymer. Stretching transformed the unmelted lamellar crystals into shishkebab fibers that acted as a scaffold for an elastomeric matrix of entangled, amorphous chains. Density measurements indicated that the process did not significantly affect the amount of crystallinity, which was about 23%. If the specimen was recrystallized by cooling after it recovered from the stretched state, the amount of orientation decreased with increasing stretching temperature. However , if recrystallization occurred in the stretched state, it led to the formation of a second crystalline network that prevented contraction of the oriented crystalline structure during strain recovery. It was suggested that the second network was anchored by a 0-PP daughter lamellae that crystallized epitaxially on the a-PP mother crystals of the extended fibrils. Although the manner in which the films were stretched and recrystallized strongly affected the modulus, good elasticity of the stretched films revealed the persistence of an elastomeric network. V

Journal of Applied Polymer Science, 2003

ABSTRACT The orientation of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films with differe... more ABSTRACT The orientation of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films with different morphologies were studied by wide-angle X-ray diffraction. Different structures were obtained by thermally treating biaxially stretched PEN samples. Virgin and thermally treated (1 h at 240, 250, and 260°C) samples of PEN bioriented films were characterized by DSC to determine the glass-transition temperature and the crystallinity ratio. To define the orientation of crystallites in the 25 μm thick bioriented samples, pole figures were recorded for various PEN samples, as a function of their position in the transverse drawing direction. The significant result is that there is a dominant crystal population, whose c-axis direction varies from +45° at one sample edge to −45° at the other edge, the orientation at the center being parallel to the transverse direction. There is also a secondary population, which can be seen only near the center. DSC studies also showed that by increasing the annealing temperature the crystallinity ratio was increased and pole figures showed that the texture was modified, probably because of disorientation mainly from an annealing temperature of 260°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2224–2232, 2003

Journal of Applied Polymer Science, 2002

We investigated the possibility of obtaining high-density polyethylene (PE) samples with crystals... more We investigated the possibility of obtaining high-density polyethylene (PE) samples with crystals in a broad range of thicknesses. PE samples solidified by slow cooling were subjected to hydrostatic pressure at room temperature and then heated to the region of mobile pseudohexagonal form, without being passed through melting. The chains were allowed to rearrange for a period of time to a more extended chain conformation, forming larger crystals. During cooling under pressure, the transformation to orthorhombic crystals of larger thickness occurred. The thickness of the crystals was then controlled by pressure, temperature, and annealing time at high temperatures. The temperature and the pressure in the high-pressure cell was maintained at constant level within 230-295°C and 260-630 MPa, respectively. In this way, we transformed under pressure chain-folded PE crystals to partly chain-extended crystals with peak melting temperatures up to 144.85°C. A range of samples with crystals 20-160 nm thick were produced and characterized with several techniques, including wideand small-angle X-ray scattering, conventional and temperature-modulated differential scanning calorimetry, dynamic mechanical analysis, and scanning electron, atomic force, and light microscopy as well as low-frequency Raman spectroscopy. Changes in crystallographic unit cell dimensions were observed for crystals with different thicknesses. Crystallinity degree increased with increases in the lamellar thickness up to some level. The initial spherulitic structure deteriorated due to a multifold increase in the lamellar thickness. Oriented samples subjected to annealing in the pseudohexagonal region did not lose the crystal orientation while crystals grew thicker and the crystallinity degree increased; however, no drastic change to noncrystalline phase topology and structure was noticed.

Macromolecular Symposia, 2000