Anders Hult - Academia.edu (original) (raw)
Papers by Anders Hult
Surface modification of cellulose substrates by ring-opening polymerization for biocomposite appl... more Surface modification of cellulose substrates by ring-opening polymerization for biocomposite applications.
Journal of the American Chemical Society, 2009
There is an emerging interest in the development of sustainable materials with high performance. ... more There is an emerging interest in the development of sustainable materials with high performance. Cellulose is promising in this regard as it is a renewablere source with high specific properties, which can be utilized as strong reinforcements in novel biocomposites. However, to fully exploit the potential ofcellulose, its inherent hydrophilic character has to be modified in order toimprove the compatibility and interfacial adhesion with the more hydrophobicpolymer matrices commonly used in composites.In this study, the grafting of poly(e-caprolactone) (PCL) and poly(L-lactide)(PLLA) from cellulose surfaces, via ring-opening polymerization (ROP) of e-caprolactone and L-lactide, was investigated. Both macroscopic and nano-sizedcellulose were explored, such as filter paper, microfibrillated cellulose (MFC),MFC-films, and regenerated cellulose spheres. It was found that thehydrophobicity of the cellulose surfaces increased with longer graft lengths, andthat polymer grafting rendered a smoother surface morphology.To improve the grafting efficiency in the ROP from filter paper, both covalent(bis(methylol)propionic acid, bis-MPA) and physical pretreatment (xyloglucanbisMPA)were explored. The highest grafting efficiency was obtained with ROPfrom the bis-MPA modified filter papers, which significantly increased amountof polymer on the surface, i.e. the thickness of the grafted polymer layer.MFC was grafted with PCL to different molecular weights. The dispersability innon-polar solvent was obviously improved for the PCL grafted MFC, incomparison to neat MFC, and the stability of the MFC suspensions was better maintained with longer grafts. PCL based biocomposites were prepared from neat MFC and PCL grafted MFCwith different graft lengths. The polymer grafting improved the mechanical properties of the composites, and the best reinforcing effect was obtained when PCL grafted MFC with the longest grafts were used as reinforcement.A bilayer laminate consisting of PCL and MFC-films grafted with different PCL graft lengths displayed a gradual increase in the interfacial adhesion with increasing graft length.The effect of grafting on the adhesion was also investigated via colloidal probeatomic force microscopy at different temperatures and time in contact. A significant improvement in the adhesion was observed after polymer grafting.
Activated Dopamine Derivatives as Promising Primers for Adhesive-Patch Fixation of Bone Fractures
PEG-based hydrogels with well-defined network structures via UV-induced thiol-ene coupling : Synt... more PEG-based hydrogels with well-defined network structures via UV-induced thiol-ene coupling : Synthesis and characterization
The structure evolution and build-up of internal stresses in an acrylate and an epoxy cured above... more The structure evolution and build-up of internal stresses in an acrylate and an epoxy cured above their ultimate T{sub g}`s have been investigated. The samples were cured isothermally and the structure evolvement followed using a parallel plate dynamic mechanical analyzer. From the dynamic-mechanical data a predicted stress build-up was calculated and compared with an experimentally observed stress level. The predictions show that the acrylate is expected to build up stresses two orders of magnitude greater than the opoxy. This discrepancy can be explained by the difference in structure and reaction mechanism between the monomers, notably the early gelation, high rubbery modulus and high cure shrinkage of the acrylates as compared to the epoxy. In the case of the acrylate the predicted stress level agrees well with experimental results. For the epoxy no stresses were observed, presumably due to their being below the measurability limit.
A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril n... more A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril networks
The goal of this work was to synthesize complex macromolecular architectures such as dendrimers a... more The goal of this work was to synthesize complex macromolecular architectures such as dendrimers and dendronized polymers, and evaluate the effect from the dendrons on the optical and material properties. The work presented in this doctoral thesis, Dendrimers and Dendronized Polymers - Synthesis and Characterization, is divided into one minor and one major part. The first part deals with the synthesis and characterization of two sets of dendritic porphyrins based on 2,2-bis(methylol)propionic acid (bis-MPA). The second part deals with the synthesis and characterization of dendronized poly(hydroxyl ethyl methacylate), dendronized poly(norbornene), and dendronized triblock copolymers, were the pendant dendrons are based on bis-MPA. Both free-base and zinc containing dendritic porphyrins was synthesized up to the fifth generation by employing iterative ester coupling utilizing the acetonide protected anhydride of bis-MPA as generic building block. First and second generation dendron bearing methacrylates based on 2-hydroxyethyl methacrylate were also synthesized by utilizing the acetonide protected anhydride of bis-MPA, and subsequently polymerized by atom transfer radical polymerization. By adopting a divergent “graft-to” approach starting from the first generation dendronized poly(hydroxyl ethyl methacrylate), well-defined dendronized polymers with acetonide, hydroxyl, acetate and hexadecyl surface functionality were obtained. By utilizing the same divergent iterative esterfication, first to fourth generation dendron functionalized norbornenes were synthesized. These monomers were polymerized by ring-opening metathesis polymerization, utilizing either Grubbs´ first or second generation catalyst. Acrylate functional first to fourth generation monomers were synthesized by the copper(I) catalyzed “click” coupling of azido functional dendrons and propargyl acrylate. The monomers were polymerized to dendronized triblock copolymers by reversible addition-fragmentation chain transfer polymerization, utilizing a difunctional poly(methyl methacrylate) as macro chain transfer agent. The bulk properties of the dendronized poly(hydroxyl ethyl methacrylate) and poly(norbornene) were investigated by dynamic rheological measurements and differential scanning calorimetry. It was found that all the acetonide functional bis-MPA based dendronized polymers had glass transitions temperatures in a similar range. The rheological behaviour showed that for the dendronized polymers having the same backbone length the complex viscosity as a function of functionality was independent of the surface functionality of the polymer. The generation number of the polymer had a profound influence on the complex viscosity, changing form a Newtonian behaviour to a shear thinning behaviour when the generation of the dendrons was increased from two to four. The dendronized poly(norbornene) had increasingly shorter backbone lengths for each generational increase, and for the materials set with comparably lower degree of polymerization, the G’ part of the complex modulus was mostly affected by attaching larger dendrons. In the case of the sample set of higher degree of polymerization, the second, third, and fourth generation samples had similar slopes of the G’ and G” curves, indicating a similar relaxation behaviour.
Acs Symposium Series, Oct 15, 1996
The development of time-dependent properties with conversion during cure of step-wise reacting ep... more The development of time-dependent properties with conversion during cure of step-wise reacting epoxy and chain-wise reacting acrylate coatings has been investigated. Using a torsional dynamic mechanical analyser, dynamic shear modulus and change in sample thickness was ...
Macromolecular Rapid Communications, Aug 1, 1999
Thermally initiated cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane was ... more Thermally initiated cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane was carried out using benzyltetramethylenesulfonium hexafluoroantimonate as initiator. The resulting hydroxy-functional polyether was thoroughly analyzed by 1 H and 13 C NMR spectroscopy and found to have a hyperbranched architecture with a degree of branching of 0.4. The polyether was successfully employed as a multifunctional initiator for e-caprolactone. Molecular weight measurements on the polyether showed a narrow molecular weight distribution analyzed by SEC and MALDI-TOF (1.3 and 1.4, respectively).
Polymer, Jul 1, 1996
Butylvinyl ether, 4-ethoxyphenyl 4-[4-(vinyloxy)butyloxy]benzoate and 4-ethoxyphenyl 4[ll-(vinylo... more Butylvinyl ether, 4-ethoxyphenyl 4-[4-(vinyloxy)butyloxy]benzoate and 4-ethoxyphenyl 4[ll-(vinyloxy)undecyloxy]benzoate have been polymerized using boron trifluoride diethyl etherate and tin tetrachloride as cationic initiator. Polymers produced at different temperatures and with different solvents exhibited different stereoregularities. Dyad resonances were assigned from the 0-methylene absorption in a decoupled 13C nuclear magnetic resonance spectrum, assuming that the polymerization proceeded according to the first-order Markovian trial. The liquid crystalline side-chain polymers were characterized by differential scanning calorimetry, hot-stage polarized light microscopy and X-ray diffraction in order to study the influence of tacticity on mesomorphism and organization. The polymers based on 4-ethoxyphenyl 4111-(vinyloxy)undecyloxy]benzoate with different tacticities exhibited the same interdigitated smectic A and B structures. Recorded differences in isotropization temperatures could be attributed to differences in molar mass.
Macromolecular Symposia, 1994
The synthesis of the following monofunctional and bifunctional liquid crystalline pvinylphenoxy-b... more The synthesis of the following monofunctional and bifunctional liquid crystalline pvinylphenoxy-based monomers is described: 4-methoxyphenyl 4-[ 1 1-(4-~inylphenoxy)-undecy1oxy)lbenzoate (l), 4-cyanophenyl 4-[ 1 1-(4-vinylphenoxy)undecyloxy]benzoate (2) and 3-(4-vinylphenoxy)propyl 444-[ 1 1-(4-vinylphenoxy)undecyloxy] benzoy1oxy)benzoate (3). Both free radical and cationic polymerization of the monofunctional monomers 1 and 2 yielded side-chain liquid crystalline polymers exhibiting smectic A mesomorphism. The polymers exhibited high molar masses (m,, = 40000-100000 g/mol) and relatively narrow molar mass distributions (aw/&!& between 1.5 and 3). Ordered thin films were prepared by in-situ photopolymerization of monomers 1,2 and 3 oriented in their nematic mesophases. Thin films of a thermally stabilized ordered side-chain liquid crystalline polymer were prepared by copolymerization of the monofunctional monomer 1 and the bifunctional monomer 3, the latter present in low concentration. The films regained orientation when cooled down from temperatures above the isotropization point (1 37 "C) as evidenced by polarized FT-Raman measurements.
![Research paper thumbnail of Smectic A organisation in copolymers of i-butyl vinyl ether and 11-[(4?-cyano-4-biphenyl)oxy]undecanyl vinyl ether as assessed by X-ray scattering](https://attachments.academia-assets.com/119268201/thumbnails/1.jpg)
](Polymer Bulletin, Nov 1, 1995
Liquid crystalline copoly(vinyl ether)s based on i-butyl vinyl ether and ll-[(4'-cyano-4-biphenyl... more Liquid crystalline copoly(vinyl ether)s based on i-butyl vinyl ether and ll-[(4'-cyano-4-biphenyl)oxy]undecanyl vinyl ether of various compositions were synthesized. The copolymers exhibited smectic A mesomorphism with a layer thickness strongly increasing with increasing i-butyl vinyl ether content. The intermesogenic distance remained unchanged. A model of the layer structures is given based on structural assessments from small-angle X-ray scattering data.
Polymer Bulletin, 1991
... various functional groups H. Jonsson 2, V. Percec 1'*, and A. Hult 2 1Department of Macr... more ... various functional groups H. Jonsson 2, V. Percec 1'*, and A. Hult 2 1Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH 44124, USA 2Department of Polymer Technology, The Royal Institute of Technology, S-100 44 Stockholm, ...
Surface modification of cellulose substrates by ring-opening polymerization for biocomposite appl... more Surface modification of cellulose substrates by ring-opening polymerization for biocomposite applications.
Journal of the American Chemical Society, 2009
There is an emerging interest in the development of sustainable materials with high performance. ... more There is an emerging interest in the development of sustainable materials with high performance. Cellulose is promising in this regard as it is a renewablere source with high specific properties, which can be utilized as strong reinforcements in novel biocomposites. However, to fully exploit the potential ofcellulose, its inherent hydrophilic character has to be modified in order toimprove the compatibility and interfacial adhesion with the more hydrophobicpolymer matrices commonly used in composites.In this study, the grafting of poly(e-caprolactone) (PCL) and poly(L-lactide)(PLLA) from cellulose surfaces, via ring-opening polymerization (ROP) of e-caprolactone and L-lactide, was investigated. Both macroscopic and nano-sizedcellulose were explored, such as filter paper, microfibrillated cellulose (MFC),MFC-films, and regenerated cellulose spheres. It was found that thehydrophobicity of the cellulose surfaces increased with longer graft lengths, andthat polymer grafting rendered a smoother surface morphology.To improve the grafting efficiency in the ROP from filter paper, both covalent(bis(methylol)propionic acid, bis-MPA) and physical pretreatment (xyloglucanbisMPA)were explored. The highest grafting efficiency was obtained with ROPfrom the bis-MPA modified filter papers, which significantly increased amountof polymer on the surface, i.e. the thickness of the grafted polymer layer.MFC was grafted with PCL to different molecular weights. The dispersability innon-polar solvent was obviously improved for the PCL grafted MFC, incomparison to neat MFC, and the stability of the MFC suspensions was better maintained with longer grafts. PCL based biocomposites were prepared from neat MFC and PCL grafted MFCwith different graft lengths. The polymer grafting improved the mechanical properties of the composites, and the best reinforcing effect was obtained when PCL grafted MFC with the longest grafts were used as reinforcement.A bilayer laminate consisting of PCL and MFC-films grafted with different PCL graft lengths displayed a gradual increase in the interfacial adhesion with increasing graft length.The effect of grafting on the adhesion was also investigated via colloidal probeatomic force microscopy at different temperatures and time in contact. A significant improvement in the adhesion was observed after polymer grafting.
Activated Dopamine Derivatives as Promising Primers for Adhesive-Patch Fixation of Bone Fractures
PEG-based hydrogels with well-defined network structures via UV-induced thiol-ene coupling : Synt... more PEG-based hydrogels with well-defined network structures via UV-induced thiol-ene coupling : Synthesis and characterization
The structure evolution and build-up of internal stresses in an acrylate and an epoxy cured above... more The structure evolution and build-up of internal stresses in an acrylate and an epoxy cured above their ultimate T{sub g}`s have been investigated. The samples were cured isothermally and the structure evolvement followed using a parallel plate dynamic mechanical analyzer. From the dynamic-mechanical data a predicted stress build-up was calculated and compared with an experimentally observed stress level. The predictions show that the acrylate is expected to build up stresses two orders of magnitude greater than the opoxy. This discrepancy can be explained by the difference in structure and reaction mechanism between the monomers, notably the early gelation, high rubbery modulus and high cure shrinkage of the acrylates as compared to the epoxy. In the case of the acrylate the predicted stress level agrees well with experimental results. For the epoxy no stresses were observed, presumably due to their being below the measurability limit.
A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril n... more A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril networks
The goal of this work was to synthesize complex macromolecular architectures such as dendrimers a... more The goal of this work was to synthesize complex macromolecular architectures such as dendrimers and dendronized polymers, and evaluate the effect from the dendrons on the optical and material properties. The work presented in this doctoral thesis, Dendrimers and Dendronized Polymers - Synthesis and Characterization, is divided into one minor and one major part. The first part deals with the synthesis and characterization of two sets of dendritic porphyrins based on 2,2-bis(methylol)propionic acid (bis-MPA). The second part deals with the synthesis and characterization of dendronized poly(hydroxyl ethyl methacylate), dendronized poly(norbornene), and dendronized triblock copolymers, were the pendant dendrons are based on bis-MPA. Both free-base and zinc containing dendritic porphyrins was synthesized up to the fifth generation by employing iterative ester coupling utilizing the acetonide protected anhydride of bis-MPA as generic building block. First and second generation dendron bearing methacrylates based on 2-hydroxyethyl methacrylate were also synthesized by utilizing the acetonide protected anhydride of bis-MPA, and subsequently polymerized by atom transfer radical polymerization. By adopting a divergent “graft-to” approach starting from the first generation dendronized poly(hydroxyl ethyl methacrylate), well-defined dendronized polymers with acetonide, hydroxyl, acetate and hexadecyl surface functionality were obtained. By utilizing the same divergent iterative esterfication, first to fourth generation dendron functionalized norbornenes were synthesized. These monomers were polymerized by ring-opening metathesis polymerization, utilizing either Grubbs´ first or second generation catalyst. Acrylate functional first to fourth generation monomers were synthesized by the copper(I) catalyzed “click” coupling of azido functional dendrons and propargyl acrylate. The monomers were polymerized to dendronized triblock copolymers by reversible addition-fragmentation chain transfer polymerization, utilizing a difunctional poly(methyl methacrylate) as macro chain transfer agent. The bulk properties of the dendronized poly(hydroxyl ethyl methacrylate) and poly(norbornene) were investigated by dynamic rheological measurements and differential scanning calorimetry. It was found that all the acetonide functional bis-MPA based dendronized polymers had glass transitions temperatures in a similar range. The rheological behaviour showed that for the dendronized polymers having the same backbone length the complex viscosity as a function of functionality was independent of the surface functionality of the polymer. The generation number of the polymer had a profound influence on the complex viscosity, changing form a Newtonian behaviour to a shear thinning behaviour when the generation of the dendrons was increased from two to four. The dendronized poly(norbornene) had increasingly shorter backbone lengths for each generational increase, and for the materials set with comparably lower degree of polymerization, the G’ part of the complex modulus was mostly affected by attaching larger dendrons. In the case of the sample set of higher degree of polymerization, the second, third, and fourth generation samples had similar slopes of the G’ and G” curves, indicating a similar relaxation behaviour.
Acs Symposium Series, Oct 15, 1996
The development of time-dependent properties with conversion during cure of step-wise reacting ep... more The development of time-dependent properties with conversion during cure of step-wise reacting epoxy and chain-wise reacting acrylate coatings has been investigated. Using a torsional dynamic mechanical analyser, dynamic shear modulus and change in sample thickness was ...
Macromolecular Rapid Communications, Aug 1, 1999
Thermally initiated cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane was ... more Thermally initiated cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane was carried out using benzyltetramethylenesulfonium hexafluoroantimonate as initiator. The resulting hydroxy-functional polyether was thoroughly analyzed by 1 H and 13 C NMR spectroscopy and found to have a hyperbranched architecture with a degree of branching of 0.4. The polyether was successfully employed as a multifunctional initiator for e-caprolactone. Molecular weight measurements on the polyether showed a narrow molecular weight distribution analyzed by SEC and MALDI-TOF (1.3 and 1.4, respectively).
Polymer, Jul 1, 1996
Butylvinyl ether, 4-ethoxyphenyl 4-[4-(vinyloxy)butyloxy]benzoate and 4-ethoxyphenyl 4[ll-(vinylo... more Butylvinyl ether, 4-ethoxyphenyl 4-[4-(vinyloxy)butyloxy]benzoate and 4-ethoxyphenyl 4[ll-(vinyloxy)undecyloxy]benzoate have been polymerized using boron trifluoride diethyl etherate and tin tetrachloride as cationic initiator. Polymers produced at different temperatures and with different solvents exhibited different stereoregularities. Dyad resonances were assigned from the 0-methylene absorption in a decoupled 13C nuclear magnetic resonance spectrum, assuming that the polymerization proceeded according to the first-order Markovian trial. The liquid crystalline side-chain polymers were characterized by differential scanning calorimetry, hot-stage polarized light microscopy and X-ray diffraction in order to study the influence of tacticity on mesomorphism and organization. The polymers based on 4-ethoxyphenyl 4111-(vinyloxy)undecyloxy]benzoate with different tacticities exhibited the same interdigitated smectic A and B structures. Recorded differences in isotropization temperatures could be attributed to differences in molar mass.
Macromolecular Symposia, 1994
The synthesis of the following monofunctional and bifunctional liquid crystalline pvinylphenoxy-b... more The synthesis of the following monofunctional and bifunctional liquid crystalline pvinylphenoxy-based monomers is described: 4-methoxyphenyl 4-[ 1 1-(4-~inylphenoxy)-undecy1oxy)lbenzoate (l), 4-cyanophenyl 4-[ 1 1-(4-vinylphenoxy)undecyloxy]benzoate (2) and 3-(4-vinylphenoxy)propyl 444-[ 1 1-(4-vinylphenoxy)undecyloxy] benzoy1oxy)benzoate (3). Both free radical and cationic polymerization of the monofunctional monomers 1 and 2 yielded side-chain liquid crystalline polymers exhibiting smectic A mesomorphism. The polymers exhibited high molar masses (m,, = 40000-100000 g/mol) and relatively narrow molar mass distributions (aw/&!& between 1.5 and 3). Ordered thin films were prepared by in-situ photopolymerization of monomers 1,2 and 3 oriented in their nematic mesophases. Thin films of a thermally stabilized ordered side-chain liquid crystalline polymer were prepared by copolymerization of the monofunctional monomer 1 and the bifunctional monomer 3, the latter present in low concentration. The films regained orientation when cooled down from temperatures above the isotropization point (1 37 "C) as evidenced by polarized FT-Raman measurements.
Polymer Bulletin, Nov 1, 1995
Liquid crystalline copoly(vinyl ether)s based on i-butyl vinyl ether and ll-[(4'-cyano-4-biphenyl... more Liquid crystalline copoly(vinyl ether)s based on i-butyl vinyl ether and ll-[(4'-cyano-4-biphenyl)oxy]undecanyl vinyl ether of various compositions were synthesized. The copolymers exhibited smectic A mesomorphism with a layer thickness strongly increasing with increasing i-butyl vinyl ether content. The intermesogenic distance remained unchanged. A model of the layer structures is given based on structural assessments from small-angle X-ray scattering data.
Polymer Bulletin, 1991
... various functional groups H. Jonsson 2, V. Percec 1'*, and A. Hult 2 1Department of Macr... more ... various functional groups H. Jonsson 2, V. Percec 1'*, and A. Hult 2 1Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH 44124, USA 2Department of Polymer Technology, The Royal Institute of Technology, S-100 44 Stockholm, ...