Glaser coupling of polymers: Side‐reaction in Huisgens “click” coupling reaction and opportunity for polymers with focal diacetylene units in combination with ATRP

Atom transfer radical polymerization (ATRP) was used in combination with Glaser type coupling, allowing the clean and efficient formation of symmetrically coupled polymers with a central diacetylene unit. The feasibility of the clean acetylene coupling was investigated with alkyne terminated poly(ethylene glycol) and poly(styrene) obtained by ATRP. The latter allowed subsequent ATRP to be carried out from the coupled products, offering opportunities for the formation of well defined functional materials with central diacetylene units. Glaser coupling was also observed as a side reaction in Huisgens‐type “click” reactions of polymeric alkynes with hindered surface azide groups. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3795–3802, 2009     

Surface modification of multiwalled carbon nanotubes with biocompatible polymers via ring opening and living anionic surface initiated polymerization. Kinetics and crystallization behavior

Multiwalled carbon nanotubes (MWNTs) were functionalized with 2‐hydroxyethyl benzocyclobutene (BCB‐EO) through a Diels–Alder cycloaddition reaction. The functionalized MWNTs were utilized for the surface initiated ring opening (ROP) catalyzed and anionic polymerization of ε‐caprolactone (ε‐CL) and ethylene oxide (EO), respectively. The kinetics of the ROP of ε‐CL was monitored through thermogravimetric analysis (TGA) which revealed that the polymerization proceeds very fast as compared to that of EO and that both polymerizations could be controlled with time. ¹H NMR, Raman and FTIR spectroscopy, TGA, DSC, and transmission electron microscopy (TEM) were employed for the characterization of these polymer/CNT hybrids. DSC results showed that a remarkable nucleation effect is produced by MWNTs that reduced the supercooling needed for crystallization of both PεCL and PEO. Furthermore, the isothermal crystallization kinetics of the grafted PεCL and PEO was substantially accelerated compared to the neat polymers. The strong impact on the nucleation and crystallization kinetics is attributed to the covalent MWNT‐polymer bonding. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4379–4390, 2009     

Surface modification of multiwalled carbon nanotubes via nitroxide‐mediated radical polymerization

The nitroxide‐mediated radical polymerization of styrene was carried out on the surfaces of multiwalled carbon nanotubes (MWNTs) initiated by an MWNT‐supported initiator multiwalled carbon nanotube–2″,2″,6″,6″‐tetramethylpiperidinyloxy (MWNT–Tempo). The content of polystyrene grafted from the surface was controlled by changes in the polymerization conditions, such as the reaction times or the ratios of monomers to initiators. The obtained polystyrene‐grafted multiwalled carbon nanotubes (MWNT–PSs) were further used to initiate the polymerization of 4‐vinylpyridine to get polystyrene‐b‐poly(4‐vinylpyridine)‐grafted multiwalled carbon nanotubes (MWNT–PS‐b‐P4VPs). In contrast to unmodified MWNTs, MWNT–PSs had relatively good dispersibility in various organic solvents, such as tetrahydrofuran, CHCL₃, and o‐dichlorobenzene. The structures and properties of MWNT–PSs and MWNT–PS‐b‐P4VPs were characterized and studied with several methods, including thermogravimetric analysis, Fourier transform infrared, ultraviolet–visible, and transmission electron microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4656–4667, 2006     

A convenient room temperature polycondensation toward hyperbranched AB2‐type all‐aromatic polyesters with phenol terminal groups

As a convenient alternative to the classical melt polycondensation the one‐pot solution polycondensation of suitable AB₂ monomers under mild conditions has been successfully adapted to hyperbranched all‐aromatic polyester with phenol terminal groups. The polymerization was performed in solution at room temperature directly using commercially available 3,5‐dihydroxybenzoic acid as monomer and 4‐(dimethylamino) pyridinium 4‐tosylate as catalyst to suppress the formation of N‐acylurea. Different carbodiimides as coupling agents were investigated to find the optimal esterification conditions. The polymers have been characterized extensively and were compared with their well‐known analogs synthesized in melt. The characterization was carried out by NMR spectroscopy, size exclusion chromatography, and asymmetric flow‐field flow fractionation as an alternative separation technique for multifunctional polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5158–5168, 2009     

Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)

Multiwall carbon nanotube (MWNT) was grafted with polyacrylate‐g‐poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid‐treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880–6887, 2006     

A novel synthesis of polymer brush on multiwall carbon nanotubes bearing terminal monomeric unit

A novel approach to fabricate polymer brushes on the surface of carbon nanotubes (CNTs) is proposed. Carboxyl groups on the surface of chemically oxidized CNTs were reacted with hexamethylene diisocyanate, followed by a reaction with methacrylamide to give terminal vinyl groups‐functionalized CNTs, so called “CNT‐mer.” The synthetic procedure was investigated step‐by‐step and the synthesized CNT‐mer was used to grow polystyrene (PS) from CNTs by a simple in situ polymerization in the presence of a thermal initiator. By employing ¹H NMR, X‐ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and light scattering, the experimental results were verified. Using this approach, 45% PS with respect to CNTs are grafted on the surface of CNTs with about 4.0 nm thickness. This novel technique would provide a facile route to prepare tailor‐made polymer brushes on the surface of CNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:6394–6401, 2006     

Carbon nanotubes in emulsion‐templated porous polymers: Polymer nanoparticles,sulfonation, and conductivity

Sulfonated polymers are of interest for ion exchange resins, reaction supports, and membranes for separation, filtration, fuel cells, and electrochemical devices. Sulfonic groups have been introduced into polystyrene (PS) through exposure to sulfuric acid, and carbon nanotubes (CNTs) have been added to polymers to enhance proton conductivity without creating an electronic percolation pathway. PolyHIPEs, emulsion‐templated porous polymers with highly interconnected hierarchical open‐cell porous structures, are synthesized through polymerization in the external phases of high internal phase emulsions (HIPEs). In this article, the synthesis of PS‐based CNT‐filled polyHIPEs, their structure, sulfonation, and conductivity are described. Adding CNT dispersions to the HIPEs produced polymer nanoparticle–covered polyHIPEs from polymerization within the water‐soluble surfactant micelles in the internal aqueous phase droplets. The CNTs migrated from the HIPE's aqueous phase droplets into the HIPE's organic phase and formed interconnected bundles within the polyHIPE walls, reflecting a reduction in the surfactant's ability to disperse the CNTs. The water adsorption in the hygroscopic sulfonated polyHIPEs increased the conductivity by several orders of magnitude. The conductivity of the sulfonated polyHIPE containing CNTs was more than an order of magnitude greater than that of the sulfonated polyHIPEs with no CNTs. The CNTs act as “bridges,” enhancing the connection between existing conductive pathways. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4369–4377     

Characterization and electrical properties of polypyrrole/multiwalled carbon nanotube composites synthesized by in situ chemical oxidative polymerization

This study describes the preparation of polypyrrole (PPy)/multiwalled carbon nanotube (MWNT) composites by in situ chemical oxidative polymerization. Various ratios of MWNTs, which served as hard templates, were first dispersed in aqueous solutions with the surfactant cetyltrimethylammonium bromide to form micelle/MWNT templates and overcome the difficulty of MWNTs dispersing into insoluble solutions of pyrrole monomer, and PPy was then synthesized via in situ chemical oxidative polymerization on the surface of the templates. Raman spectroscopy, Fourier transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the fabricated composites. Structural analysis using FESEM and HRTEM showed that the PPy/MWNT composites were core (MWNT)–shell (PPy) tubular structures. Raman and FTIR spectra of the composites were almost identical to those of PPy, supporting the idea that MWNTs served as the core in the formation of a coaxial nanostructure for the composites. The conductivities of these PPy/MWNT composites were about 150% higher than those of PPy without MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1413–1418, 2006     

Synthesis of new graft copolymers containing polyisobutylene by a combination of the 1,1‐diphenylethylene technique and cationic polymerization

The synthesis of macroinitiators for the cationic polymerization of isobutylene via radical polymerization is presented. The 1,1‐diphenylethylene system was used to obtain macroinitiators consisting of 4‐chloromethylstyrene and methyl methacrylate units. The resulting polymers were used for the cationic polymerization of isobutylene, yielding graft copolymers that were characterized by gel permeation chromatography and NMR. The dependence of the molar mass and polydispersity on the temperature and monomer concentration was studied. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3725–3733, 2002     

Preparation and characterization of nematic polyazomethine/single‐walled carbon nanotube composites prepared by in situ polymerization

The synthesis and characterization of a series of nematic SWNT‐polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt‐extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2361–2372, 2009     

Jacketed polymers: Controlled synthesis of mesogen‐jacketed polymers and block copolymers

The controlled radical polymerization of mesogen‐jacketed liquid crystalline polymers has triggered great interests in synthesis of complex structures as well as well‐defined linear homopolymers with controlled molecular weight and narrow molecular weight distributions. This review highlights the synthetic strategies of controlled radical polymerization of linear homopolymers, star polymers, superbranched polymers, graft polymers, block copolymers, star block copolymers, and so on. The employed living methods include nitroxide‐mediated radical polymerization and atom transfer radical polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 319–330, 2009     

“Radical‐controlled” oxidative polymerization of phenol: Comparison with that of 4‐phenoxyphenol

“Radical‐controlled” oxidative polymerization of phenol (p‐1) by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane)copper(II) catalyst was performed and compared with that of 4‐phenoxyphenol (p‐2) in detail. Although the coupling selectivity for p‐1 seemed to be controlled by the catalyst, the C? C coupling, which was excluded completely for p‐2, occurred to some extent. The initial reaction rate of p‐1 was much smaller than that of p‐2, leading to the difference of polymerization behavior between p‐1 and p‐2. The rate‐determining step would be the coupling of controlled radicals species from the ESR measurement of the reaction mixture. The polymer resulting from p‐1 consisted mainly of phenylene oxide units, but had no crystallinity in contrast to the crystalline polymer from p‐2. However, the present polymer showed the highest thermal stability in the polymers obtained by oxidative polymerization of p‐1. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1955–1962, 2005     

Solvent‐induced self‐assembly in cardanol‐based urethane methacrylate comb polymers

We report side chain urethane–methacrylate comb polymers based on the renewable resource cardanol and its saturated analogue 3‐pentadecyl phenol and their self‐assembly into pores, spheres, vesicles, tubes, and so forth. The monomers were synthesized in one pot by coupling 1 equiv. of isophorone diisocyanate with 1 equiv. of cardanol/pentadecyl phenol followed by coupling with 1 equiv. of hydroxyethyl methacrylate. They were polymerized free radically using benzoyl peroxide as the initiator and were characterized by NMR and FTIR, and their molecular weights were determined by gel permeation chromatography. The unique polymer design had sites for self‐organization via hydrogen bonding of the side chain urethane units, π–π stacking interactions of the aromatic units as well as interdigitation of the long C₁₅ alkyl side chains in the polymer. The morphologies of solvent cast polymer films were studied using microscopic techniques such as scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The polymers exhibited three‐dimensional honeycomb morphology in CHCl₃, whereas in tetrahydrofuran, they formed spheres. The direct cardanol‐derived polymer PCIH showed a tendency for multiple morphologies such as spheres and tubes in tetrahydrofuran. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2996–3009, 2009     

Synthesis of hollow crosslinked miktoarm polymer using miniemulsion as templates

Hollow crosslinked polymers (HCPs) were synthesized using arm first method via atom transfer radical polymerization. The polymerization process was performed in miniemulsion system, in which the macroinitiator, PEG‐Br, was in the water phase, whereas the vinyl‐monomer, 4‐vinylpyridine (4VP), and the crosslinker, DVB, were in the butanone phase. TEM images and light scattering characterization showed that the resultant polymer contained a hollow space, and the volume of the hollow space could be adjusted by changing the ratio of water to butanone. Also, hollow crosslinked Miktoarm polymers (HCMPs) were synthesized through this method when two different macroinitiators, PEG‐Br and PNIPAM‐Br, were used to coinitiate the polymerization of the vinyl‐monomer, 4VP and DVB. The ¹H NMR spectra showed that the hollow polymers contained both PEG arms and PNIPAM arms. The hollow morphologies of the resultant Miktoarm polymers were the same as the HCPs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1651–1660, 2009     

Facile synthesis of star‐shaped copolymers via combination of RAFT and ring opening polymerization

Reversible addition fragmentation chain transfer (RAFT) polymerization and bifunctional sparteine/thiourea organocatalyst‐mediated ring opening polymerization (ROP) were combined to produce poly(L ‐lactide) star polymers and poly(L ‐lactide‐co‐styrene) miktoarm star copolymers architecture following a facile experimental procedure, and without the need for specialist equipment. RAFT was used to copolymerize ethyl acrylate (EA) and hydroxyethyl acrylate (HEA) into poly(EA‐co‐HEA) co‐oligomers of degree of polymerization 10 with 2, 3, and 4 units of HEA, which were in turn used as multifunctional initiators for the ROP of L ‐lactide, using a bifunctional thiourea organocatalytic system. Furthermore, taking advantage of the living nature of RAFT polymerization, the multifunctional initiators were chain extended with styrene (poly((EA‐co‐HEA)‐b‐styrene) copolymers), and used as initiators for the ROP of L ‐lactide, to yield miktoarm star copolymers. The ROP reactions were allowed to proceed to high conversions (>95%) with good control over molecular weights (ca. 28,000‐230,000 g/mol) and polymer structures being observed, although the molecular weight distributions are generally broader (1.3–1.9) than those normally observed for ROP reactions. The orthogonality of both polymerization techniques, coupled with the ubiquity of HEA, which is used as a monomer for RAFT polymerization and as an initiator for ROP, offer a versatile approach to star‐shaped copolymers. Furthermore, this approach offers a practical approach to the synthesis of polylactide star polymers without a glove box or stringent reaction conditions. The phase separation properties of the miktoarm star copolymers were demonstrated via thermal analyses. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6396–6408, 2009     

Helically chiral poly(quinoxalin‐2,3‐diyl)s: Toward the synthesis of stereoregular polymeric organocatalysts

The synthesis of seven new aromatic diisocyanide monomers is described and a rationale for their stability is given, as well as their behavior in the palladium‐mediated aromatizing polymerization yielding helically chiral poly(quinoxalin‐2,3‐diyl)s (PQs). Acceleration of the otherwise slow polymerization by microwave heating was observed. The polymers are designed to display potential organocatalytically active functionalities (e.g., phenols, pyridines) nearby stereolabile biaryl axes, which are asymmetrically governed by the configurationally stable helical backbone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4830–4839, 2009     

Enhancement in solubility and conductivity of polyaniline with lignosulfonate modified carbon nanotube

An organic solvent soluble and high electrical conductivity, for example, 55.43 S/cm, polyaniline (PANI), was synthesized by a novel method. In this two steps process, a noncovalent approach was initially developed by functionalization of multiwalled carbon nanotubes (MWNTs) using calcium lignosulfonate (LsCa) via self‐assembly to result MWNTs‐LsCa. Then, the MWNT‐LsCa was employed as a template to lead anilinium monomers directly aligned on the surface to start the polymerization of PANI. The noncovalent modification of MWNTs avoided their agglomeration effectively to allow them doped in PANI at the molecular level. The obtained novel PANI/MWNTs‐LsCa presented excellent solubility and high conductivity. The recorded scanning electron microscopy photographs revealed that the MWNTs‐LsCa was wrapped with PANI chains that caused the crystal orientation improvement. In this article, a related scheme on resulting in the high conductivity of PANI/MWNTs‐LsCa was showed and described. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2036–2046, 2009     

Thermal degradation and kinetic analysis of biodegradable PBS/multiwalled carbon nanotube nanocomposites

In this study, carbon nanotubes (CNTs) were first modified using N,N′‐ dicyclohexylcarbodiimide (DCC) dehydrating agents. Subsequently, the poly(butylene succinate)/multiwalled carbon nanotube (PBS/MWNTs) nanocomposites were prepared through facile melt blending. Thermal degradation of these PBS/MWNT nanocomposites was investigated; the kinetic parameters of degradation were calculated using the Coats and Redfern, Ozawa, and Horowitz and Metzger methods, respectively. It was found that the degradation reaction mechanism of PBS and the CNT‐C18 containing nanocomposites at lower temperature was likely to produce an F1 model through reaction of random chain cleavage (cis‐elimination). However, the reaction mechanism at higher temperature was likely to be a D1 model because of the dominant diffusion control effect. Moreover, it was found that the activation energies of CNT‐C18‐containing PBS nanocomposites were first increased with the content of CNT‐C18, but then decreased after the content was larger than 0.5 wt % for all models at differing heating rates. This may be due to the formation of a conductive network of CNTs in the polymer matrix at higher content of CNTs, which lead to better heat and electrical conductivity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1231–1239, 2009     

Syndiotactic‐specific radical polymerization of N,N‐dimethylacrylamide in the presence of tartrates: A proposed mechanism for the polymerization

Radical polymerization of N,N‐dimethylacrylamide (DMAAm) was investigated in the presence of tartrates, such as diethyl L ‐tartrate, diisopropyl L ‐tartrate, and di‐n‐butyl L ‐tartrate, in toluene at low temperatures. Syndiotactic polymers were obtained in the presence of tartrates, whereas isotactic polymers were obtained in the absence of tartrates. The syndiotactic‐specificity increased with increasing amount of tartrates and with decreasing polymerization temperature. NMR analysis suggested that DMAAm and tartrates formed a 1:1 complex through double hydrogen bonding. A mechanism for the syndiotactic‐specific radical polymerization of DMAAm is proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1192–1203, 2009     

Effect of a cocatalyst modifier in the synthesis of ultrahigh molecular weight polyethylene having reduced number of entanglements

The use of a hindered phenol to trap free trimethylaluminum (TMA) in methylaluminoxane (MAO) solutions has been reported to improve the performance of single‐site, homogeneous catalysts for olefin polymerization. In the present study, with the help of rheological analyses, we have investigated and compared the molecular weight, molecular weight distribution and entanglement density of ultrahigh molecular weight polyethylene synthesized with a single‐site catalyst activated by MAO and phenol‐modified MAO. While the number average molecular weight (M_n) of the obtained polymers remains the same for both activations, a higher yield and a higher entanglement density are found in the initial stages of polymerization on using phenol‐modified MAO as the cocatalyst. These results suggest that on using the phenol‐modified MAO as activator, a higher number of active sites are obtained. Surprisingly in the presence of untreated MAO, a tail in the higher molecular mass region is produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013