Chemical modification of metallocene‐based polyolefinic elastomers by acrylic acid and its influence on physico‐mechanical properties: Effect of reaction parameters,crystallinity and pendant chain length

In this investigation, solution grafting of acrylic acid (AA) in presence of benzoyl peroxide (BPO) was carried out onto metallocene‐based “poly(ethylene‐octene) elastomers” (POE) as well as “poly(ethylene‐butene) elastomers” (PBE), to impart polarity on the non‐polar rubbery matrix and also to study the effects of crystallinity and pendant chain length on the “grafting percentage” and “percent gel yield” at optimized conditions for all the POE and PBE systems. Reaction parameters were optimized on the basis of the relative proportions of graft and gel formations obtained through %weight gain, Fourier Transform infrared spectroscopy and elemental analysis. The effect of grafting at its maximum level on various physico‐mechanical properties was also thoroughly investigated by using X‐ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical, dynamic mechanical (DMTA), and thermogravimetric analysis (TGA) and the properties were correlated with the structure of the modified polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5529–5540, 2007     

Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments

The control of hydroxylated polyethylene (PE) structures was investigated in the copolymerization of ethylene with allyl alcohol or 10-undecen-1-ol with a specific metallocene, methylaluminoxane, and trialkyl aluminum catalyst system through changes in the copolymerization conditions. The incorporation of allyl alcohol into the PE backbones was controllable through changes in the trialkyl aluminum, leading to terminally hydroxylated PE or a copolymer possessing hydroxyalkyl side chains. The copolymerization of ethylene with 10-undecen-1-ol gave copolymers with hydroxyalkyl side chains of various contents with a variety of molecular weights through changes in the copolymerization conditions. The obtained copolymers were useful as macroinitiators that allowed polar polymer segments to grow on the PE backbones, leading to the creation of graft copolymers that possessed PE and polar polymer segments. In this way, polyethylene-g-poly(propylene glycol) (PE-g-PPG) and polyethylene-g-poly(ϵ-caprolactone) (PE-g-PCL) were synthesized. The ¹³C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization, and transmission electron microscopy demonstrated nanoorder phase separation and indistinct phase boundaries. ¹³C NMR and gel permeation chromatography analyses indicated the formation of PE-g-PCL, in which 36–80 mol % of the hydroxyl groups worked as initiators for ϵ-caprolactone polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3657–3666, 2003     

Synthesis,properties, and sulfonation of novel dendritic multiblock copoly(ether‐sulfone)

Multiblock copoly(ether‐sulfone)s ( PES s) bearing anchor units for the construction of dendritic blocks were synthesized by two‐step reactions: (1) synthesis of PES block with both phenoxide end‐groups; (2) chain extension and end‐capping of the block by use of excess novel hexafunctional agent, hexakis(4‐(4‐fluorophenylsulfonyl)phenyl)benzene. The optimum average block length (n) and amount (x) of the hexafunctional agent used for the synthesis of high‐molecular‐weight PES without crosslinking were n = 26 and x = 2.6 equiv, respectively. The dendritic blocks in the PES were constructed by the aromatic nucleophilic substitution reaction of the activated aromatic fluoride groups on the anchor units using 4‐tritylbenzenethiol. The clean substitution of the fluoride groups in the PES was confirmed by ¹H NMR and ¹⁹F NMR. Three sulfonic acid groups were introduced on the pendant phenyl rings of the trityl groups in the PES by the reaction with chlorosulfonic acid. This is the first example of a dendritic PES bearing clusters of sulfonic acid groups only on the dendritic blocks. Cast films of presulfonated dendritic PES were strong and flexible, however, the membranes of sulfonated dendritic PES were brittle so that the conductivity measurements were not performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6365–6375, 2008     

Introduction of reactive functionality by the incorporation of divinylbiphenyl in ethylene copolymerization with styrene or 1‐hexene using aryloxo‐modified half‐titanocenes and MAO catalysts

An efficient introduction of vinyl group into poly (ethylene‐co‐styrene) or poly(ethylene‐co?1‐hexene) has been achieved by the incorporation of 3,3′‐divinylbiphenyl (DVBP) in terpolymerization of ethylene, styrene, or 1‐hexene with DVBP using aryloxo‐modified half‐titanocenes, Cp′TiCl₂(O?2,6‐ⁱPr₂C₆H₃) [Cp′ = Cp*, ^tBuC₅H₄, 1,2,4‐Me₃C₅H₂], in the presence of MAO cocatalyst, affording high‐molecular‐weight polymers with unimodal distributions. Efficient comonomer incorporations have been achieved by these catalysts, and the content of each comonomer could be varied by its initial concentration charged. The postpolymerization of styrene was initiated from the vinyl group remained in the side chain by treatment with n‐BuLi. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2581–2587     

Poly(triphenylamine)s derived from oxidative coupling reaction: Substituent effects on the polymerization,electrochemical, and electro‐optical properties

A series of triphenylamine‐based polymers containing electron‐donating methoxy (? OCH₃) and electron‐withdrawing cyano or nitro (? CN or ? NO₂) substituents in the main chains have been designed and investigated. These conjugated polymers ( P1 – P3 ) could be readily prepared by oxidative coupling polymerization from monomers ( M1 – M3 ) using FeCl₃ as an oxidant. The P2 and P3 exhibited moderate high T_g values (203–205 °C) and thermal stability. These polymers in NMP solution showed UV–vis absorption around 288–404 nm and photoluminescence peaks around 435–492 nm. P1 – P3 showed reversible oxidation redox couples at E_onset = 0.67, 0.99, and 1.00 V in solution of 0.1 M tetrabutylammonium perchlorate (TBAP)/acetonitrile (CH₃CN), respectively. M3 and P3 exhibited reversible reduction redox couples at E_onset = ?1.04 and ?1.03 V. These polymers also revealed electrochromic characteristic changing color at different potential. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 285–294, 2009     

Modification of polyisoprene‐block‐poly(vinyl trimethylsilane) block copolymers via hydrosilylation and hydrogenation,and their gas transport properties

Polyisoprene‐block‐poly(vinyl trimethylsilane) (PI‐b‐PVTMS) block copolymers having different isoprene contents are successfully chemically modified and characterized by proton nuclear magnetic resonance spectroscopy (¹H‐NMR), Fourier transform infrared spectroscopy, gel permeation chromatography, and thermogravimetric analysis. Gas transport properties of the initial block copolymers and their derivatives modified via hydrosilylation and hydrogenation are measured. The modified block copolymers show higher permeabilities for O₂ and H₂ than the unmodified block copolymers while maintaining similar O₂/N₂ and H₂/N₂ selectivities. Hydrosilylation and hydrogenation of block copolymers with a low isoprene content result in a permeability increase for O₂ and H₂ of 15 to 40%, respectively. Similarly, for block copolymers with high isoprene contents, increases in permeabilities up to 125% are observed compared to initial PI‐b‐PVTMS. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013 , 51, 1252–1261     

Semi‐interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers: Morphology and mechanical properties in dependence of the concentration of functional groups

Grafted semi‐interpenetrating polymer networks (IPNs) were prepared from polyurethane (PU) prepolymers with polyester soft segments and hard segments containing carboxylic functional groups as well as polymethacrylate (PM) prepolymers with tertiary amine functional groups. The dependence of morphological and mechanical properties on the concentration of functional groups was studied. The enhanced miscibility of PU and PM prepolymers was observed at concentrations of functional groups of 0.25 mmol/g of polymer and above. Despite the improved miscibility, the PM prepolymers showed a tendency toward phase separation. Because the observed glass‐transition temperature shifts of PU prepolymers indicated substantial miscibility, we ascribed this phenomenon to the presence of methyl methacrylate rich sequences in the PM prepolymer. The observed changes in mechanical properties by increasing the content of functional groups were typical for ionomers. Young's modulus increased as a result of physical interactions between functional groups. A significant drop in tensile strength was observed in IPN samples with phase‐separated PU and PM prepolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 115–123, 2002     

Poly(ethylene imine)‐graft‐poly(ethylene oxide) brush‐like copolymers: Preparation,thermal properties,and selective supramolecular inclusion complexation with α‐cyclodextrin

Poly(ethylene imine)‐graft‐poly(ethylene oxide) (PEI‐g‐PEO) copolymers were synthesized via Michael addition reaction between acryl‐terminated poly(ethylene oxide) methyl ether (PEO) and poly(ethylene imine) (PEI). The brush‐like copolymers were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the crystallinity of the PEO side chains in the copolymers remained unaffected by the PEI backbone whereas the crystal structure of PEO side chains was altered to some extent by the PEI backbone. The crystallization behavior of PEO blocks in the copolymers suggests that the bush‐shaped copolymers are microphase‐separated in the molten state. The PEO side chains of the copolymers were selectively complexed with α‐cyclodextrin (α‐CD) to afford hydrophobic side chains (i.e., PEO/α‐CD inclusion complexes). The X‐ray diffraction (XRD) shows that the inclusion complexes (ICs) of the PEO side chains displayed a channel‐type crystalline structure. It is identified that the stoichiometry of the inclusion complexation of the PEI‐g‐PEO with α‐CD is close to that of the control PEO with α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2296–2306, 2008     

Synthesis and properties of biodegradable copolymers based on 4,4′‐(adipoyldioxy)dicinnamic acid, 1,6‐hexanediol,and poly(ethylene glycol)s

4,4′‐(Adipoyldioxy)dicinnamic acid (CAC) was synthesized by a condensation of adipoyl chloride and 4‐hydroxycinnamic acid. The CAC6 copolymers were prepared by a high‐temperature solution polycondensation of a diacyl chloride of CAC, 1,6‐hexanediol (6), and poly(ethylene glycol) (PEG) in which the molecular weights of PEG are 1000, 2000, and 8300. Differential scanning calorimetric curves of the copolymers exhibited a glass‐transition temperature because of PEG moiety and two melting endotherms (T_m's); the one at the higher T_m was due to CAC6 moiety, and the other at the lower T_m was due to PEG moiety, suggesting that these copolymers are the block type. The incorporation of the PEG component decreased the tensile strength and initial modulus, but increased the elongation extremely. The enzymatic degradation was performed in phosphate buffer solution (pH 7.2) with Ps. cepacia lipase at 37 °C. The degradation rate of the copolymers increased significantly with an increasing content of PEG, which was correlated to the water absorption of the copolymers. All copolymers could undergo photocuring by ultraviolet (UV) light irradiation (λ > 280 nm) at ambient temperature, as examined by UV spectroscopy and solubility. The CAC6/E2000(50/50) film photocured for 3 min exhibited a good elastic property with a maximum tensile strength of 3.7 MPa and maximum elongation of 640%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2930–2938, 2003