Sulfonation of metallocene‐based polyolefinic elastomers and its influence on physicomechanical properties: Effect of reaction parameters,styrene grafting,and pendant chain length

Direct sulfonation and styrene‐mediated sulfonation were carried out onto metallocene‐based poly(ethylene‐co‐octene) (POE) and poly(ethylene‐co‐butene) (PBE) elastomers to impart polarity on the completely nonpolar rubbery matrices and to prepare a new class of elastomer. The influence of styrene‐grafting and pendant chain length on the degree of sulfonation was also studied. The effects of sulfonation, styrene grafting and styrene‐mediated sulfonation at their optimized levels on various physicomechanical properties were thoroughly investigated, and the resultant properties were correlated with structures of the modified elastomers. Higher extent of sulfonic acid groups were introduced through direct sulfonation in comparison with the styrene‐mediated sulfonation, whereas better thermal and mechanical properties were obtained through styrene‐mediated sulfonation in comparison with the direct sulfonation process. PBE had shown higher degree of sulfonation and percentage grafting than POE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8023–8040, 2008     

Molecular captain: A light‐sensitive linker molecule in poly(ethylene glycol)‐poly(L‐alanine)‐poly(ethylene glycol) triblock copolymer directs molecular nano‐assembly,conformation, and sol‐gel transition

We report a poly(ethylene glycol)‐poly(L ‐alanine)‐azobenzene‐poly(L ‐alanine)‐poly(ethylene glycol) (PEG‐PA‐Z‐PA‐PEG) as a temperature and light sensitive polymer. The poly(ethylene glycol)‐poly(L ‐alanine) diblock copolymers with a flexible‐rigid block structure were coupled by an azobenzene group that undergoes a reversible configurational change between “trans” and “cis” upon exposure to UV and vis light. The single azobenzene molecule embedded in the middle of a block copolymer with a flexible (shell)‐rigid (core) structure significantly affected molecular assembly, micelle size, polypeptide secondary structure, and sol‐to‐gel transition temperature of the polymer aqueous solution, depending on its exposure to UV or vis light. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Multi‐functional poly(vinylidene fluoride) graft copolymers

Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro‐electricity, and membrane forming capability. In order to tune its properties, modification through grafting from approach by atom transfer radical polymerization (ATRP) is preferred. Hydrophilic polymers like poly(ethylene glycol) methacrylate, poly(methacrylic acid), poly(dimethylaminoethyl methacrylate) (PDMAEMA), and so forth have been anchored from PVDF backbone in order to make permeation of water molecules through the PVDF based membranes. The successful solution grafting of PDMAEMA chains from PVDF backbone by ATRP resulted appreciable graft conversion and hence its bulk properties showed a significant change. This water soluble graft copolymer shows incredible mechanical and adhesive properties. PVDF‐g‐poly(n‐butyl methacrylate) generates honey‐comb porous film using “breath figure” technique. Recently, they have used further improvement of grafting where model ATRP initiators are anchored using atom transfer radical coupling and used them as macroinitiators for grafting. This approach simplified the grafting reactions even more and enabled successful grafting of a large number of monomers under relatively less drastic conditions with appreciable conversion compared with the previous conditions. This technique has resulted interesting solution properties, ion and electron conducting PVDF, antifouling membrane, super glue and super tough materials, capable of generating metal nanoparticles tunable with pH and temperature. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2569–2584     

Synthesis and characterization of novel biodegradable epoxy‐modified polyurethane elastomers

Biodegradable polyurethane elastomers with the potential for applications in medical implants were synthesized from the reaction of epoxy‐terminated polyurethane prepolymers (EUPs) with 1,6‐hexamethylenediamine as a curing agent. EUPs were themselves prepared from the reaction of glycidol and isocyanate‐terminated polyurethanes made from different molecular weights of poly(ε‐caprolactone) (CAPA) and 1,6‐hexamethylene diisocyanate. All materials were characterized by spectroscopic methods. The curing conditions were optimized by gel content measurements. The curing kinetic and kinetic parameters were determined from differential scanning calorimetry measurements. The effects of changing the crosslink density and crystallinity of elastomers via the alteration of the CAPA polyol molecular weight on the physical, mechanical, and degradation properties of the final elastomeric polymers were examined fully. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2985‐2996, 2005     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The living chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

Amphiphilic PEG‐grafted poly(ester‐carbonate)s: Synthesis and diverse nanostructures in water

Novel biodegradable amphiphilic graft copolymers containing hydrophobic poly(ester‐carbonate) backbone and hydrophilic poly(ethylene glycol) (PEG) side chains were synthesized by a combination of ring‐opening polymerization and “click” chemistry. First, the ring‐opening copolymerization of 5,5‐dibromomethyl trimethylene carbonate (DBTC) and ε‐caprolactone (CL) was performed in the presence of stannous octanoate [Sn(Oct)₂] as catalyst, resulting in poly(DBTC‐co‐CL) with pendant bromo groups. Then the pendant bromo groups were completely converted into azide form, which permitted “click” reaction with alkyne‐terminated PEG by Huisgen 1,3‐dipolar cycloadditions to give amphiphilic biodegradable graft copolymers. The graft copolymers were characterized by proton nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectra and gel permeation chromatography measurements, which confirmed the well‐defined graft architecture. These copolymers could self‐assemble into micelles in aqueous solution. The size and morphologies of the copolymer micelles were measured by transmission electron microscopy and dynamic light scattering, which are influenced by the length of PEG and grafting density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis and self‐assembly behavior of amphiphilic polypeptide‐based brush‐coil block copolymers

Synthesis and self‐assembly behavior of a novel amphiphilic brush‐coil block copolymer bearing hydrophilic poly(ethylene glycol) segment and hydrophobic polypeptide brush segment were presented in this work. The poly(γ‐benzyl‐L ‐glutamate) (PBLG) brush is synthesized through “grafting from” strategy by ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride (BLG‐NCA) initiated by the flanking terminal primary amino group of macroinitiator. The copolymers were characterized by ¹H NMR, gel permeation chromatography, Fourier transform infrared, circular dichroism spectrum, and differential scanning calorimetry. The self‐assembly behavior of the brush‐coil block copolymers in aqueous solution was investigated by means of transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and laser light scattering. Spherical micelles were observed when the length of PBLG brush is shorter. The aggregate morphology transforms to spindle‐like micelles and then to rod‐like micelles, as the length of polypeptide brush increases. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5967–5978, 2009     

Effects of solvent,casting temperature,and guest/host stoichiometries on the properties of shape memory material based on partial α‐CD‐PEG inclusion complex

A series of supramolecular inclusion complex (IC) films were formed by threading α‐cyclodextrin (α‐CD) molecules over poly(ethylene glycol) (PEG), according to the designed ratio of α‐CD/PEG. Because of containing α‐CD‐PEG inclusion crystallites as physical crosslinks and uncovered PEG crystallites as “switch phase”, the resulting supramolecular α‐CD‐PEG partial ICs displayed a shape memory effect. The properties of the materials were investigated by ¹H‐NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling measurement. It was found that the casting temperature, solvent, and the ratio of α‐CD‐PEG inclusion/PEG had great influence on the formation and properties of α‐CD‐PEG partial ICs. The modes of complexes on different conditions were proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 951–957, 2010     

New polymer organogelators with L‐isoleucine and L‐valine as a gelation‐causing segment: Organogelation by a combination of supramolecular polymer and conventional polymer

New polymer organogelators, which are composed of poly(ethylene glycol), poly(propylene glycol), and poly(dimethylsiloxane)s as a polymer segment and L ‐isoleucine and L ‐valine derivatives as a gelation‐causing segment, were synthesized, and their organogelation properties were examined in organic solvents and oils. These polymer organogelators formed organogels in many organic solvents and oils, and their gels were thermally stable and had a high mechanical strength. Furthermore, the effects of the polymer backbone on the organogelation is discussed using FTIR spectroscopy, field emission scanning electron microscope observation, and analysis of thermal stability and strength of the organogel. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 353–361, 2008     

Heterograft copolymers of poly(ε‐caprolactone) prepared by combination of ATRA “grafting onto” and ATRP “grafting from” processes

This paper aims at reporting on the synthesis of a heterograft copolymer by combining the “grafting onto” process based on atom transfer radical addition (ATRA) and the “grafting from” process by atom transfer radical polymerization (ATRP). The statistical copolymerization of ε‐caprolactone (εCL) and α‐chloro‐ε‐caprolactone (αClεCL) was initiated by 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(αClεCL‐co‐εCL) on the terminal double bond of α‐MeO,ω‐CH₂?CH? CH₂? CO₂‐poly(ethylene oxide) (PEO). The amphiphilic poly(εCL‐g‐EO) graft copolymer collected at this stage forms micelles as supported by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The unreacted pendant chloro groups of poly(εCL‐g‐EO) were used to initiate the ATRP of styrene with formation of copolymer with two populations of randomly distributed grafts, that is PEO and polystyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6015–6024, 2006     

Synthesis and solution properties of well‐defined comb‐on‐comb graft polymers

Well‐defined comb‐on‐comb copolymers of styrene, isoprene, and α‐methyl‐styrene are prepared through cascade “grafting‐onto” methods. The polymer main chain is prepared by nitroxide‐mediated radical polymerization while the branches are prepared by anionic polymerization. The “grafting‐onto” approach employs the coupling chemistry of macromolecular anions, such as polystyryllithium, polyisoprenyllithium, or poly(α‐methylstyryl)lithium, toward either benzyl chloride or epoxy ring on precursor backbones. Thus a series of ABA‐, ABB‐, and ABC‐type comb‐on‐comb copolymers are prepared and characterized by gel permeation chromatography equipped with a multi‐angle laser light scattering detector and a viscometer. Unusual “U‐shaped” dependences of radius of gyration, R_g, on molecular weight are observed for comb‐on‐comb products, which are attributable to delayed elution of the densely grafted copolymers from GPC columns. The result also shows that the comb‐on‐comb copolymers exhibit morphologies from hard sphere to cylindrical rod, depending on the length ratio of the main chain to the branches. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5518–5527, 2008     

Surface modification of UV‐cured epoxy resins by click chemistry

A novel method for surface modification of UV‐cured epoxy network was described. Photoinitiated cationic copolymerization of a bisepoxide, namely 3,4‐epoxy cyclohexylmethyl 3,4‐epoxycyclohexanecarboxylate (EEC) with epibromohydrine (EBH) by using a cationic photoinitiator, [4‐(2‐methylpropyl)phenyl]4‐methylphenyl‐iodonium hexafluorophosphate, in propylene carbonate solution was studied. The real‐time Fourier transform infrared spectroscopic, gel content determination and thermal characterization studies revealed that both EEC and EBH monomers take part in the polymerization and epoxy network possessing bromomethyl functional groups was obtained. The bromine functions of the cured product formed on the glass surface were converted to azide functionalities with sodium azide. Independently prepared alkyne functional poly(ethylene glycol) (PEG) was subsequently anchored to azide‐modified epoxy surface by a “click” reaction. Surface modification of the network through incorporation of hydrophilic PEG chain was evidenced by contact angle measurements. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2862–2868, 2010     

Interfacial interaction in EVA‐carbon nanotube and EVA‐clay nanocomposites

Proper filler‐matrix compatibility is a key factor in view of obtaining nanocomposites with well‐dispersed nanofillers displaying enhanced properties. In this respect, polymer‐filler interaction can be improved by a proper combination of matrix and nanofiller polarities. This is explored for matrices ranging from nonpolar high density poly(ethylene) to ethylene‐vinyl acetate (EVA) copolymers with varying vinyl acetate contents, in combination with several types of organoclay or carbon nanotubes. A novel in situ characterization methodology using modulated temperature differential scanning calorimetry is presented to evaluate the matrix‐filler interaction. During quasi‐isothermal crystallization of the matrix, an “excess” contribution is observed in the recorded heat capacity signal because of reversible melting and crystallization. Its magnitude considerably decreases upon addition of nanofiller in case of strong interfacial interaction, whereas the influence is moderate in case of a less interacting matrix‐filler combination. It is suggested that the “excess heat capacity” can be used to quantify the segmental mobility of polymer chains in the vicinity of the nanofiller. Hence it provides valuable information on the strength of interaction, governed by the physical and chemical nature of matrix and filler. Heating experiments subsequent to quasi‐isothermal crystallization point at a certain degree of molecular ordering, responsible for crystal nucleation in EVA copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1291–1302, 2007     

Preparation and properties of 1,2‐polybutadiene grafting with poly(1,3‐butadiene)‐block‐(dimethylsiloxane)

The development of silica‐filling elastomers with high mechanical performance and good processability is still a great challenge. In this study, we fabricated siloxane‐grafted atactic 1,2‐polybutadiene (1,2‐PB) rubber through grafting poly(1,3‐butadiene)‐block‐(dimethylsiloxane) (PB‐b‐PDMS) onto 1,2‐PB molecular chains by coordination polymerization using a molybdenum (Mo)‐based catalyst system. The PB‐b‐PDMS with active double bonds was synthesized by anionic polymerization. Fourier transform infrared analysis (FTIR), elementary analysis, and GPC‐MALLS‐viscometer analyses verified the incorporation of PB‐b‐PDMS and the grafting structure in the resulting polymer. Scanning electron microscope (SEM), bound rubber testing, and dynamic mechanical analysis demonstrated that the graft‐modification with PB‐b‐PDMS improved silica dispersity in the 1,2‐PB matrix because the incorporation of siloxane groups provided stronger interfacial interaction with silica. Meanwhile, the graft‐modified 1,2‐PB exhibited lower Mooney viscosity, higher tensile strength, and lower heat build‐up than unmodified 1,2‐PB. This concept provides novel inspiration for the preparation of advanced rubber with promoted silica compatibility and mechanical performance.     

Diels–Alder modification of poly(ethylene terephthalate‐co‐anthracene‐2,6‐carboxylate) with N‐substituted maleimides

Dimethyl 2,6‐anthracene dicarboxylate is used as a comonomer in the synthesis of functional copolymers that are subject to modification with Diels–Alder reactions. The formation of poly(ethylene terephthalate‐co‐2,6‐anthracenate), containing less than 20 mol % of the anthracene‐2,6‐dicarboxylate structural units, provides materials that are tractable and soluble. The anthracene units of the copolymers undergo Diels–Alder reactions with N‐substituted maleimides. The grafting of N‐alkylmaleimides affords soluble, hydrophobic polymers, whereas grafting with maleimide‐terminated poly(ethylene glycol) affords hydrophilic polymers. Because this reaction proceeds below the melting point of the copolymers, the procedure can be applied to thin films, whereby the surface properties are modified. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3256–3263, 2002     

Supramolecular Silicone Elastomers with Healable and Hydrophobic Properties Crosslinked by “Salt‐Forming Vulcanization”

In this article, supramolecular silicone elastomers with self‐healing function were first prepared by simple and controllable “salt‐forming vulcanization” of polyaminopropylmethylsiloxane with acids. Their structures and micrographs were verified by Fourier transform infrared spectra, Small‐angle X‐ray scattering experiments and atomic force microscope. The experimental results showed that the ion‐association complexes were formed during vulcanization, and the obtained elastomers displayed self‐healing and good mechanical properties even if the cross‐linking agent was excessed. The thermogravimetric analysis showed that the elastomers crosslinked by inorganic acid were stable under high temperature. Unexpectedly, bionic structures were observed in the elastomers, which further changed the hydrophobicity of the surfaces of the elastomers physically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 903–911     

Synthesis and characterization of water‐soluble gold nanoparticles stabilized by comb‐shaped copolymers

The water‐soluble gold nanoparticles stabilized by well‐defined comb‐shaped copolymers have been synthesized successfully. The hybrid nanoparticles consist of gold core and poly[poly(ethylene oxide) methyl ether acrylate]‐block‐poly(N‐isopropylacrylamide) [P(A‐MPEO)‐block‐PNIPAM] shell. The water‐soluble comb‐shaped copolymers, P(A‐MPEO)‐block‐PNIPAM with PNIPAM as a handle, were successfully synthesized via a macromonomer technique using reversible addition fragmentation chain transfer (RAFT) polymerization method. The terminal dithioester group of the comb‐shaped copolymer was reduced to a thiol end group forming SH‐terminated copolymers, P(A‐MPEO)‐block‐PNIPAM‐SH. Successively they were used to stabilize gold nanoparticles by the “grafting‐to” approach. The hybrid nanoparticles were characterized by TEM, UV–vis, and HRTEM. Because of the thermosensitive property of PNIPAM in aqueous solution, the comblike copolymer‐tethered gold nanoparticles show a sharp and reversible phase transition at 30 °C in aqueous solution, which was determined by microdifferential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 341–352, 2008     

Combining “click” chemistry and step‐growth polymerization for the generation of highly functionalized polyesters

Aliphatic polyesters bearing pendant alkyne groups were successfully prepared by step‐growth polymerization of different building blocks such as adipic acid and succinic acid in combination with an acetylene‐based diol, 2‐methyl‐2‐propargyl‐1,3‐propanediol, besides 1,4‐butanediol and ethylene glycol. It was demonstrated that the alkyne groups survive the high reaction temperatures (200 °C) in the presence of a radical inhibitor. The alkyne loading has been tuned by the ratio of the different monomers used, up to 25 mol % of alkyne groups. Subsequently, the alkyne groups have been reacted with azides by the copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, a popular type of “click” chemistry. “Click” reactions have been performed quantitatively in the presence of benzyl azide and azide‐terminated poly(ethylene glycol), yielding brush copolymers in the latter case. Kinetic investigations about this click reaction have been performed by means of on‐line Fourier transform mid‐infrared spectroscopy, which was reported for the first time in the field of the click chemistry research. A whole range of functionalized polyesters, based on poly(ethylene succinate) and poly(butylene adipate), is available, the properties of which can be tailored by choosing the appropriate azide compound. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6552–6564, 2008     

Microwave assisted hydroxyalkylamidation of poly(ethylene‐co‐acrylic acid) and formation of grafted poly(ϵ‐caprolactone) side chains

The microwave assisted amidation of poly(ethylene‐co‐acrylic acid) (PEAA) with 2‐(2‐aminoethoxy)ethanol was performed to yield a hydroxy functionalized poly(ethylene) based copolymer (PEAAOH) in a single step. PEAAOH was used as a polyinitiator for the ring‐opening polymerization of ε‐caprolactone. The obtained graft copolymers were studied via ¹H NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, polarized optical microscopy, and scanning electron microscopy. Microscopy methods show a crystallization behavior of banded spherulites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3659–3667, 2007     

Efficient synthesis of monodisperse,highly crosslinked,and “living” functional polymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization

The facile and efficient one‐pot synthesis of monodisperse, highly crosslinked, and “living” functional copolymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization (ILRPP) is described for the first time. The simple introduction of iniferter‐induced “living” radical polymerization (ILRP) mechanism into precipitation polymerization system, together with the use of ethanol solvent, allows the direct generation of such uniform functional copolymer microspheres. The polymerization parameters (including monomer loading, iniferter concentration, molar ratio of crosslinker to monovinyl comonomer, and polymerization time and scale) showed much influence on the morphologies of the resulting copolymer microspheres, thus permitting the convenient tailoring of the particle sizes by easily tuning the reaction conditions. In particular, monodisperse poly(4‐vinylpyridine‐co‐ethylene glycol dimethacrylate) microspheres were prepared by the ambient temperature ILRPP even at a high monomer loading of 18 vol %. The general applicability of the ambient temperature ILRPP was confirmed by the preparation of uniform copolymer microspheres with incorporated glycidyl methacrylate. Moreover, the “livingness” of the resulting polymer microspheres was verified by their direct grafting of hydrophilic polymer brushes via surface‐initiated ILRP. Furthermore, a “grafting from” particle growth mechanism was proposed for ILRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013