Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerization

Macroporous functionalized polymer beads of poly(4‐vinylpyridine‐co‐1,4‐divinylbenzene) [P(VPy‐co‐DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier‐free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy‐co‐DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10–50 μm, and the pore size was 0.1–1.5 μm. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873–880, 2003     

Crosslinked poly(ester anhydride)s based on poly(ε‐caprolactone) and polylactide oligomers

Resorbable poly(ester anhydride) networks based on ε‐caprolactone, L ‐lactide, and D,L ‐lactide oligomers were synthesized. The ring‐opening polymerization of the monomers yielded hydroxyl telechelic oligomers, which were end‐functionalized with succinic anhydride and reacted with methacrylic anhydride to yield dimethacrylated oligomers containing anhydride bonds. The degree of substitution, determined by ¹³C NMR, was over 85% for acid functionalization and over 90% for methacrylation. The crosslinking of the oligomers was carried out thermally with dibenzoyl peroxide at 120 °C, leading to polymer networks with glass‐transition temperatures about 10 °C higher than those of the constituent oligomers. In vitro degradation tests, in a phosphate buffer solution (pH 7.0) at 37 °C, revealed a rapid degradation of the networks. Crosslinked polymers based on lactides exhibited high water absorption and complete mass loss in 4 days. In ε‐caprolactone‐based networks, the length of the constituent oligomer determined the degradation: PCL5‐AH, formed from longer poly(ε‐caprolactone) (PCL) blocks, lost only 40% of its mass in 2 weeks, whereas PCL10‐AH, composed of shorter PCL blocks, completely degraded in 2 days. The degradation of PCL10‐AH showed characteristics of surface erosion, as the dimensions of the specimens decreased steadily and, according to Fourier transform infrared, labile anhydride bonds were still present after 90% mass loss. © 2003 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3788–3797, 2003     

Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid

The precipitation of Fe₃O₄ from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003     

Nucleobase-induced supramolecular polymerization in the solid state

Supramolecular polymerization, that is, the self-assembly of polymer-like materials through the utilization of the noncovalent bond, has been a developing area of research over the last decade. In this article, we report the synthesis of nucleobase-terminated (N⁶-anisoyl-adenine and thymine) low-molecular-weight poly(tetrahydrofuran) macromonomers (<2000 g mol⁻¹). The adenine-derived supramolecular telechelic polymer self-assembled in the solid state to yield materials with film- and fiber-forming capabilities. This material was thermally reversible and exhibited a ceiling temperature, above which a drop in viscosity was observed and fibers could no longer be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3589–3596, 2003     

Mechanical property tuning of semicrystalline network polymers by controlling rates of crystallization and crosslinking

Semicrystalline network polymers were obtained by the Diels–Alder (DA) reaction of furyl‐telechelic poly(ε‐caprolactone) and tris(2‐maleimide ethyl)amine. Controlling the rates of crystallization and crosslinking reaction gave materials with various properties. Curing at a temperature much below T_m of poly(ε‐caprolactone), at which crystallization proceeded first followed by DA reaction, gave a hard and stiff material, whereas curing above T_m gave a soft and stretchable one. When crystallization and crosslinking were promoted simultaneously, tough and ductile materials were obtained. Structural analysis of the network polymers showed that the variation in the properties was derived from the difference in the crystallinity, crystallite size, and network structure. Therefore, materials with various mechanical properties, from soft to hard, could be obtained by simple thermal treatment. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Tailoring of block copolymers based on the stoichiometric control of the end‐functionality of telechelic oligomers and the utilization of large‐scale fractionation by phase fluctuation chromatography: A synthetic strategy for the preparation of end‐functionalized poly(L‐lactide)‐block‐poly(oxyethylene)

An AB diblock copolymer of poly(L ‐lactide) (PLLA) and poly(oxyethylene) (PEG) with a cinnamate terminal in the PEG block was prepared by the copolymerization of L ‐lactide and partially end‐modified PEG followed by fractionation. The first step was the terminal modification of PEG with cinnamoyl chloride (CC), in which the degree of cinnamoylation of the hydroxyl terminals of PEG was roughly controlled by the feed ratio of both reactants. The resultant PEG cinnamate was subjected to copolymerization with L ‐lactide to produce a mixture of unreacted PEG dicinnamate (C‐PEG‐C), the diblock copolymer (PLLA‐PEG‐C), and the triblock copolymer (PLLA‐PEG‐PLLA) corresponding to the three components of the PEG cinnamate. This mixture was separated by phase fluctuation chromatography (PFC) to obtain PLLA‐PEG‐C in sufficient purity. This process, involving the stoichiometric control of the terminal reaction of telechelic oligomers and the utilization of PFC for fractionation, can be an efficient method for synthesizing end‐functionalized diblock copolymers from readily available telechelic oligomers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2405–2414, 2000     

Green polymer chemistry: Telechelic poly(ethylene glycol)s via enzymatic catalysis

This article reports our discovery that poly(ethylene glycol) (PEG) can quantitatively be functionalized by transesterification using Candida antarctica lipase B (Novozyme 435) as the catalyst. α‐ω telechelic PEG‐methacrylates and PEG‐acetates were successfully prepared using commercially available PEGs with both narrow and broad molecular weight distribution. ¹H and ¹³C NMR together with MALDI‐TOF mass spectroscopy verified the expected structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3024–3028, 2008     

Siliceous mesocellular foam for high-performance liquid chromatography: Effect of morphology and pore structure

Spherical siliceous mesocellular foam (MCF) particles with an average particle size of 4.8 μm have been successfully prepared. These spherical particles were tailored in pore sizes and surface areas. They were functionalized with C₈ or C₁₈ groups, and applied towards reversed phase high-performance liquid chromatography (HPLC) column separations. Their high surface areas gave rise to very good retention characteristics, as illustrated in the separation of a series of alkylbenzene solutes with increasing chain length. The highly interconnected porous structure and ultralarge pore size of MCF allowed the columns to be used at high flow rates without much loss in column efficiency. The column efficiency and peak symmetry were further improved by eliminating the micropores of the stationary phase. The reversed phase column packed with C₁₈-modified spherical MCF particles provided for excellent separation of different deoxynucleosides, illustrating the broad applicability of these materials due to their controlled pore size.     

Amphiphilic and hydrophobic surface patterns generated from hyperbranched fluoropolymer/linear polymer networks: Minimally adhesive coatings via the crosslinking of hyperbranched fluoropolymers

Hyperbranched fluoropolymers (HBFPs), based on benzyl ether linkages and having a large number of pentafluorophenyl chain ends, were crosslinked by a reaction with diamino-terminated poly(ethylene glycol) (PEG) or diamino-terminated poly(dimethyl siloxane) (PDMS) to form hyperbranched–linear copolymer networks of different compositions, structures, and properties. The crosslinking reactions involved the nucleophilic aromatic substitution of the pentafluorophenyl para-fluorines of HBFP by the amine functionalities of the respective telechelic linear segments. The contact angles, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, and atomic force microscopy (AFM) were used to characterize the resulting network film samples. The surface wettability of the crosslinked materials was affected by the nature and amount of the linear polymer crosslinking agent employed. Amphiphilic polymer networks were formed by the incorporation of diamino-terminated PEG as a crosslinker, whereas diamino-terminated PDMS produced polymer networks of a hydrophobic character. The mechanical properties improved upon crosslinking, as measured by tensile testing. The mechanical integrity of the films was also found to improve upon crosslinking, as measured by AFM machining protocols. The AFM images revealed topographical morphologies that appeared to be the result of phase segregation of HBFP from PEG or PDMS; the dimensions of the phase-segregated domains were dependent on the stoichiometry of HBFP to the linear polymer and the thickness of the coating. As the content of PEG increased, fouling by human fibrinogen, used as a model protein, decreased. Further studies are in progress to determine the effects of the surface composition, morphology, and topography on the biofouling characteristics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3531–3540, 2003     

Latex particles bearing hydrophilic grafted hairs with controlled chain length and functionality synthesized by reversible addition–fragmentation chain transfer

A method is described for synthesizing latex particles with anchored hairs by the grafting of hydrophilic chains, synthesized by reversible addition–fragmentation chain transfer, onto functionalized latex particles. These have the potential to bind biologically active species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1188–1195, 2003     

Degradable poly(ethylene oxide) hydrogels formed by crosslinking with tert‐butylperoxybenzoate

Poly(ethylene oxide) (PEO, number‐average molecular weight: 2,000,000) was crosslinked by reaction with t‐butylperoxybenzoate in the melt. Upon swelling in water, the resulting hydrogels were acidic and suggested clear evidence of spontaneous hydrolysis that continued over periods of several weeks to give clear and low‐viscosity aqueous solutions of PEO oligomers. In contrast, in neutral media the gels did not show any signs of hydrolysis. As shown by UV, IR, and size exclusion chromatographic analysis, the PEO hydrolysis products consist of benzoic acid and hydroxyl‐ and carboxyl end‐functionalized low‐molecular‐weight PEOs. This is consistent with the acid‐catalyzed hydrolysis of acetal‐, orthoester‐, and similar end‐functionalized PEOs formed by radical coupling of various PEO radicals with benzoate, alkoxy, and other radicals. Titration of the hydrolysis mixtures indicated that the total molar amount of acid exceeds that of the maximum amount of benzoic acid produced during gel formation. However, the amount of benzoic acid equaled this maximum amount. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 520–527, 2003     

Multifunctional coupling agents: Synthesis and model reactions

New multifunctional coupling agents with one 2‐oxazoline group, one oxazinone group, and one allyl ether group were prepared. It was shown by means of model reactions that under the conditions of reactive extrusion, the 2‐oxazoline group and the oxazinone group reacted selectively with carboxylic groups and amino groups, respectively. The allyl ether group remained unaffected under the reaction conditions chosen. As a model reaction, the conversion of the coupling agents with 11‐aminoundecanoic acid resulted in the formation of an allyloxy‐functionalized poly(ester amide). The reaction could be performed stepwise, in the course of which the reaction of the amino group proceeded at 110 °C in solution, whereas the reaction of the carboxylic group was performed in the melt at 220 °C. Furthermore, the utilization of the coupling agents for the preparation of telechelic poly(propylene glycol) with one oxazoline group and one allyl ether group on each chain end was described. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 655–667, 2003     

The use of poly(alkylene oxide)s to achieve fast and controlled photochromic switching in rigid matrices

We report a conjugation system for the enhancement of photochromic dye performance in rigid matrices using widely available, cheap, chemically robust and compatible polymeric starting materials, namely poly(propylene oxide) (PPO) and poly(1,2‐butylene oxide). Conjugation of these soft (low T_g) polymers to an indeno‐fused naphthopyran photochromic dye, in a telechelic geometry, gives access to a wide range of accelerated and tuned fade speeds (decoloration) via variation in molecular weight. The t_1/2 and t_3/4 fade speeds for PPO conjugates (polymer molecular weights ranging between ca. 425 and 2000) are accelerated by 35–58 and 51–76%, respectively, compared with the nonconjugated control dye. Longer oligomers provide faster decoloration approaching that obtained in solution. The stability of the polyethers allows functionalization using a wide variety of chemistries, including harsh acid catalyzed transformations, providing an overall facile synthesis of photochromic dye‐polymer conjugates in high yield and purity. In addition, these polymers give easy access to conjugates with star‐type architectures, which provide an even further improvement in performance compared with their linear counterparts with less conjugated polymer needed per dye to achieve a given fade speed. © 2012 Commonwealth of Australia. J Polym Sci Part A: Polym Chem, 2012     

Friedel–crafts reactions of pendant vinyl groups in macroporous monosized poly(meta‐divinylbenzene) and poly(para‐divinylbenzene) particles

Residual vinyl groups in macroporous monosized polymer particles of poly(meta‐DVB) and poly(para‐DVB) prepared with toluene and 2‐EHA as porogens have been reacted with aluminum chloride as Friedel–Crafts catalyst with and without the presence of lauroyl chloride. In the reaction between aluminum chloride and pendant vinyl groups a post‐crosslinking by cationic polymerization takes place. A reaction occurring simultaneously is the addition of HCl to the double bonds. The progress of these reactions was studied by characterization of vinyl group conversion, pore size distribution, specific surface area, morphology, and swelling behavior. In the reaction with aluminum chloride the poly(para‐DVB) particles showed a substantially higher conversion of pendant vinyl groups than the particles made of poly(meta‐DVB) independent of porogen type. The reaction with aluminum chloride led to a reduced swelling in organic solvents and an increased rigidity of the particles prepared with toluene as porogen. This is confirmed by an increase in the total pore volume in the dry state and a change in the pore size distribution of these particles. Also in the reaction with lauroyl chloride poly(para‐DVB) particles have shown a higher conversion of pendant vinyl groups than poly(meta‐DVB) particles and the acylation was almost complete at the early stage of the reaction. The swelling in organic solvents is reduced as a result of the incorporation of acyl groups into the particles prepared with toluene as porogen. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1366–1378, 2000     

End‐group functionalization and postpolymerization modification of helical poly(isocyanide)s

This contribution presents the synthesis of helical alkyne‐terminated polymers using a functionalized Nickel complex to initiate the polymerization of menthylphenyl isocyanides. The resulting polymers display low dispersities and controlled molecular weights. Copper‐catalyzed azide/alkyne cycloadditions (CuAAC) are performed to attach various azide‐containing compounds to the polymer termini. After azido‐phosphonate moiety attachment the polymer displays a signal at 25.4 ppm in the ³¹P NMR spectrum demonstrating successful end‐group functionalization. End‐group functionalization of a fluorescent dye allows to determine the functionalization yield as 89% (±8). Successful ligation of an azide‐functionalized peptide sequence (M_KLA = 1547 g/mol) increases the M_n from 5100 for the parent polymer to 6700 for the bioconjugate as visualized by GPC chromatography. Analysis by CD spectroscopy confirms that the helical conformation of the poly(isocyanide) block in the peptide–polymer conjugate is maintained after postpolymerization modification. These results demonstrate an easy, generalizable, and versatile strategy toward mono‐telechelic helical polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2766–2773     

Evidence of mechanisms occurring in thermally induced phase separation of polymeric systems

Thermally induced phase separation is a fabrication technique for porous polymeric structures. By means of easy‐to‐tune processing parameters, such as system composition and demixing temperature, a vast latitude of average pore dimensions, pore size distributions, and morphologies can be obtained. The relation between demixing temperature and morphology was demonstrated via cloud point curve measurement and foams fabrication with controlled thermal protocols, for the model system poly‐l ‐lactide–dioxane–water. The morphologies obtained at a temperature lower than cloud point showed a closed‐pore architecture, suggesting a “nucleation‐and‐growth” separation mechanism, which produced larger pores at higher holding times. Conversely, the porous structures attained when holding the sample above the cloud point exhibited open pores with dimensions independent of time, denoting a phase separation occurring during sample freezing. Finally, the influence of the cooling rate on final morphology was investigated, showing a clear correlation with microstructure and pore size. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 979–983     

Triblock Copolymer Based on Poly(propylene oxide) and Poly(1‐[11‐acryloylundecyl]‐3‐methyl‐imidazolium bromide)

The controlled atom transfer radical polymerization of an ionic liquid, 1‐(11‐acryloylundecyl)‐3‐methyl imidazolium bromide (ILBr), from both ends of a telechelic poly(propylene oxide) (PPO) macroinitiator, end‐functionalized with bromoisobutyryloyl is reported. The resulting highly water‐soluble triblock, poly(ILBr‐b‐PO‐b‐ILBr) is multistimuli responsive. This new class of triblocks exhibits classical surface activity in lowering surface tension at the air–water interface and in modifying wetting in waterborne coatings. It also immunizes model colloids against coagulation induced by Debye–Hückel (indifferent electrolyte) electrostatic screening. Further, sol–gel thermoreversibility is unexpectedly found as an additional form of stimuli responsiveness.     

Synthesis of poly[N‐isopropylacrylamide‐g‐poly(ethylene glycol)] with a reactive group at the poly(ethylene glycol) end and its thermosensitive self‐assembling character

Poly[N‐isopropylacrylamide‐g‐poly(ethylene glycol)]s with a reactive group at the poly(ethylene glycol) (PEG) end were synthesized by the radical copolymerization of N‐isopropylacrylamide with a PEG macromonomer having an acetal group at one end and a methacryloyl group at the other chain end. The temperature dependence of the aqueous solutions of the obtained graft copolymers was estimated by light scattering measurements. The intensity of the light scattering from aqueous polymer solutions increased with increasing temperature. In particular, at temperatures above 40°C, the intensity abruptly increased, indicating a phase separation of the graft copolymer due to the lower critical solution temperature (LCST) of the poly(N‐isopropylacrylamide) segment. No turbidity was observed even above the LCST, and this suggested a nanoscale self‐assembling structure of the graft copolymer. The dynamic light scattering measurements confirmed that the size of the aggregate was in the range of several tens of nanometers. The acetal group at the end of the PEG graft chain was easily converted to the aldehyde group by an acid treatment, which was analyzed by ¹H NMR. Such a temperature‐induced nanosphere possessing reactive PEG tethered chains on the surface is promising for new nanobased biomedical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1457–1469, 2006     

Amino‐functionalized latex particles obtained by a multistep method: Development of a new immunoreagent

Cationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one, two or three steps, monodisperse cationic latex particles to be used as the seed were synthesized. In the third and fourth steps, the amino‐functionalized monomer aminoethylmethacrylate hydrochloride was used to synthesize the final functionalized latex particles. Three different azo initiators 2,2′‐azobisisobutyramidine dihydrochloride, 2,2′‐azobisdimethylenisobutyramidine dihydrochloride, and 2,2′‐azobisisobutyronitrile were used as initiators. Hexadecyltrimethylammonium bromide was the emulsifier. To characterize the final latices, conversions were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by conductimetric titrations. Colloidal aspects were ascertained by measuring the electrophoretic mobilities. Activation of these particles with glutaraldehyde produced an efficient reagent for latex‐enhanced immunoassay. The covalent coupling efficiency (protein covalently bound with respect to the total amount of protein adsorbed) was compressed between 50 and 80%. The developed immunoreagent was applied to the measurement of serum ferritin concentration in a new turbidimetric procedure that was compared with a commercial nephelometric method; the results obtained with both methods demonstrated that the two procedures correlated well (r = 0.992). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2404–2411, 2003     

Pore structure and glass transition temperature of nanoporous poly(ether imide)

The effect of nanopores on the glass transition temperature (T_g) of poly(ether imide) was studied with differential scanning calorimetry. Nanoporous poly(ether imide) samples were obtained through the phase separation of immiscible blends of poly(ether imide) and polycaprolactone diol and by the removal of the dispersed minor phase domains with a selective solvent. Microscopy and statistical methods were used to characterize the pore structure and obtain the pore structure parameters. The pore size was found to depend on the processing time and the initial blend composition, mainly because of phase-coarsening kinetics. A decrease in T_g was observed in the nanoporous poly(ether imide) in comparison with the bulk samples. The change in T_g was strongly influenced by the pore structure and was explained by the percolation theory. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3546–3552, 2006