Functional copolymer/organo‐MMT nanoarchitectures. VII. Interlamellar controlled/living radical copolymerization of maleic anhydride with butyl methacrylate via preintercalated RAFT agent–organoclay complexes

We have developed a new approach for the synthesis of polymer nanocomposites using a bifunctional reversible addition–fragmentation chain transfer (RAFT) agent, two types of organo‐montmorillonites (O‐MMT), such as a non‐reactive dimethyldidodecyl ammonium (DMDA)‐MMT and a reactive octadecyl amine (ODA)‐MMT organoclays, maleic anhydride (MA), and n‐butyl methacrylate (BMA) monomers and a radical initiator. This method includes the following stages: (1) synthesis of RAFT intercalated O‐MMTs by a physical or chemical interaction of the RAFT agent having two pendant carboxylic groups [S,S′‐bis(α,α′‐dimethyl‐α″‐acetic acid) trithiocarbonate] with surface alkyl amines of O‐MMT containing tertiary ammonium cation or primary amine groups through strong H‐bonding and compexing/amidization reactions, respectively, and (2) utilization of these well dispersed and intercalated RAFT…O‐MMT complexes and amide derivative of RAFT…ODA‐MMT as new modified RAFT agents in radical‐initiated interlamellar controlled/living complex‐radical copolymerization of MA‐BMA monomer pair. Nanostructure and compositions of the synthesized RAFT…O‐MMT complexes and functional copolymer/O‐MMT hybrids were confirmed by FTIR, GPC, XRD, thermal (DSC‐TGA), SEM, and TEM morphology analyses. This simple and versatile method can be applied to a wide range of monomer/comonomer systems for the preparation of completely exfoliated macromolecular nanoarchitectures. Copyright © 2011 John Wiley & Sons, Ltd.     

Asymmetric cyclopolymerization of N‐tert‐butyl‐N‐allylacrylamide in the presence of β‐cyclodextrin

The radical polymerization of N‐tert‐butyl‐N‐allylacrylamide (t‐BAA) was carried out in a dimethyl sulfoxide/H₂O mixture in the presence of β‐cyclodextrin (β‐CD). The polymerization proceeded with the complete cyclization of the t‐BAA unit and yielded optically active poly(t‐BAA). The IR spectrum of the obtained polymer showed that the cyclic structure in the polymer was a five‐membered ring. The optical activity of poly(t‐BAA) increased with an increasing molar ratio of β‐CD to the t‐BAA monomer. The interaction of β‐CD with t‐BAA was confirmed by ¹H NMR and ¹³C NMR analyses of the polymerization system. It is suggested that interaction of the t‐BAA monomer with the hydrophobic cavity of β‐CD plays an important role in the asymmetric cyclopolymerization of t‐BAA. The radical copolymerization of t‐BAA with styrene (St), methyl methacrylate, ethyl methacrylate, or benzyl methacrylate (BMA) also produced optically active copolymers with a cyclic structure from the t‐BAA unit. St and BMA carrying a phenyl group were predicted to compete with t‐BAA for interaction with β‐CD in the copolymerization system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2098–2105, 2000     

Reversible addition–fragmentation transfer (RAFT) copolymerization of methyl methacrylate and styrene in miniemulsion

In the reversible addition–fragmentation transfer (RAFT) copolymerization of two monomers, even with the simple terminal model, there are two kinds of macroradical and two kinds of polymeric RAFT agent with different R groups. Because the structure of the R group could exert a significant influence on the RAFT process, RAFT copolymerization may behave differently from RAFT homopolymerization. The RAFT copolymerization of methyl methacrylate (MMA) and styrene (St) in miniemulsion was investigated. The performance of the RAFT copolymerization of MMA/St in miniemulsion was found to be dependent on the feed monomer compositions. When St is dominant in the feed monomer composition, RAFT copolymerization is well controlled in the whole range of monomer conversion. However, when MMA is dominant, RAFT copolymerization may be, in some cases, out of control in the late stage of copolymerization, and characterized by a fast increase in the polydispersity index (PDI). The RAFT process was found to have little influence on composition evolution during copolymerization. The synthesis of the well‐defined gradient copolymers and poly[St‐b‐(St‐co‐MMA)] block copolymer by RAFT miniemulsion copolymerization was also demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6248–6258, 2004     

Composition control of copolymer in semibatch emulsion copolymerization. II. MMA/styrene/BMA three‐component system

In this study, polymers of the MMA/Styrene/BMA three‐component system were synthesized through either soapless semibatch emulsion copolymerization or soapless batch emulsion copolymerization technique. The optimal monomer feed flow rate was determined from the interphase partition laws, monomer reactivity ratios, and three or four times of iterative experimental procedures through semibatch emulsion copolymerization. As a result, the instantaneous composition of polymers could also be effectively controlled to get the desired final products. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3253–3269, 2000     

Synthesis of star‐shaped copolymers with methyl methacrylate and n‐butyl methacrylate by metal‐catalyzed living radical polymerization: Block and random copolymer arms and microgel cores

Various star‐shaped copolymers of methyl methacrylate (MMA) and n‐butyl methacrylate (nBMA) were synthesized in one pot with RuCl₂(PPh₃)₃‐catalyzed living radical polymerization and subsequent polymer linking reactions with divinyl compounds. Sequential living radical polymerization of nBMA and MMA in that order and vice versa, followed by linking reactions of the living block copolymers with appropriate divinyl compounds, afforded star block copolymers consisting of AB‐ or BA‐type block copolymer arms with controlled lengths and comonomer compositions in high yields (≥90%). The lengths and compositions of each unit varied with the amount of each monomer feed. Star copolymers with random copolymer arms were prepared by the living radical random copolymerization of MMA and nBMA followed by linking reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 633–641, 2002; DOI 10.1002/pola.10145     

Investigation of the radical copolymerization and terpolymerization of maleic anhydride and norbornenes by an in situ 1H NMR analysis of kinetics and by the mercury method: Evidence for the lack of charge‐transfer‐complex propagation

The radical copolymerization of electron‐deficient maleic anhydride (MA) and electron‐rich norbornene (NB) derivatives with 2,2′‐azobis(isobutyronitrile) (AIBN) in dioxane‐d₈ has been monitored in situ by ¹H NMR spectroscopy with free induction decays recorded every 30 min at 60, 70, or 84 °C. The ratios of the monomer pairs were varied in some cases. The NB derivatives employed in this study included bicyclo[2.2.1]hept‐2‐ene (NB), t‐butyl 5‐norbornene‐2‐carboxylate, methyl 5‐norbornene‐2‐methyl‐2‐carboxylate, and ethyl tetracyclo[4.4.0.1^2,5.1^7,10]dodec‐3‐ene‐8‐carboxylate. Decomposition of AIBN, consumption of the monomers, feed ratios, endo/exo ratios, copolymer compositions, and copolymer yields were studied as a function of polymerization time. Furthermore, a homopolymerizable third monomer (t‐butyl methacrylate, methacrylic acid, t‐butyl acrylate, or acrylic acid) was added to the NB/MA 1/1 system, revealing that the methacrylic monomer polymerizes rapidly in the early stage and that the ratio of MA to NB in the terpolymer strongly deviates from 1/1. In contrast, however, the acrylic monomers are more uniformly incorporated into the polymer. Nevertheless, these studies indicate that MA and NB do not always behave as a pair in radical polymerization and disproves the commonly believed charge‐transfer mechanism. Electron‐deficient fumaronitrile was also included in the kinetics study. To further understand the copolymerization mechanism, MA and NB were competitively reacted with a cyclohexyl radical generated by the treatment of cyclohexylmercuric chloride with sodium borohydride (mercury method). A gas chromatographic analysis of the reaction mixtures has revealed that a cyclohexyl radical reacts with MA almost exclusively in competition and that the cyclohexyl adduct of MA essentially accounts for all the products in a mass balance experiment, eliminating a possibility of the formation of an adduct involving the MA–NB charge‐transfer complex. Thus, the participation of a charge‐transfer complex in the copolymerization of MA and NB cannot be important. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3521–3542, 2000     

Synthesis and characterization of thiophene‐substituted N‐phenyl maleimide polymers by photoinduced radical polymerization

Two types of novel functionalized N‐[4‐(4′‐hydroxyphenyloxycarbonyl)phenyl]maleimide and N‐(4‐{[2‐(3‐thienyl)acetyl]oxyphenyl}oxycarbonylphenyl)maleimide (MIThi) were synthesized starting from 4‐maleimido benzoic acid. Photoinduced radical homopolymerization of MIThi and its copolymerization with styrene were performed at room temperature to give linear polymers containing pendant thienyl moieties using ω,ω‐dimethoxy‐ω‐phenylacetophenone as an initiator. Copolymers' compositions and the equilibrium constant (K) for electron donor–acceptor complex formation suggest an alternating nature of the copolymerization. The monomer reactivity ratios and Alfrey–Price Q,e values were also determined. The thermal behavior of the new synthesized monomers and polymers was investigated by differential scanning calorimetry and thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 995–1004, 2002     

Copper(0)‐mediated living radical polymerization of acrylonitrile at room temperature

The copper(0)‐catalyzed living radical polymerization of acrylonitrile (AN) was investigated using ethyl 2‐bromoisobutyrate as an initiator and 2,2′‐bipyridine as a ligand. The polymerization proceeded smoothly in dimethyl sulphoxide with higher than 90% conversion in 13 h at 25 °C. The polymerization kept the features of controlled radical polymerization. ¹H NMR spectra proved that the resultant polymer was end‐capped by ethyl 2‐bromoisobutyrate species. Such polymerization technique was also successfully introduced to conduct the copolymerization of styrene (St) and AN to obtain well‐controlled copolymers of St and AN at 25 °C, in which the monomer conversion of St could reach to higher than 90%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Terpolymerization of maleic anhydride, trans-stilbene and acrylic monomers

The results of radical terpolymerization of maleic anhydride (MA), trans-stilbene (Stb) and acrylic monomers (n-butyl methacrylate (BMA) and acrylonitrile (AN)) as acceptor-donor-acceptor monomer systems are discussed. The structure and composition of terpolymers are determined by chemical (acid number for MA units) and elemental (content of N for AN units and O for BMA units) analyses, as well as by FTIR spectroscopy through recorded analytical absorption bands for MA (1770 and 1845 cm⁻¹), Stb (864 cm⁻¹) and BMA (1730 cm⁻¹) units, respectively. The considerable change in the terpolymer compositions is observed when a strong acceptor MA is substituted with BMA (or AN), having comparatively low acceptor character in the system studied. Copolymerization constants for the MA ? Stb complex and acrylic comonomers pairs are determined according to the modified Kelen-Tüdös equation. Obtained results show that at the chosen ratios of comonomers, radical terpolymerization proceeded mainly by a true “complex” mechanism in the stage of near binary copolymerization of MA ? Stb complexed monomers with free BMA (or AN). The kinetics of terpolymerization and terpolymer compositions are studied in the low and high conversion stages. It is shown that for the MA-Stb-BMA system the dependence of R_p on the concentration of individual comonomers has extreme character, while for BMA-Stb-AN this dependence does not have similar character. This fact indicated that terpolymerization in the BMA-Stb-AN system proceeds according to a classical statistical copolymerization mechanism. The terpolymer composition-thermal behaviour relationships are also studied by differential scanning calorimetry and thermogravimetric analysis methods.     

Radical ring‐opening copolymerization behavior of vinyloxirane: Synthesis of copolymer from 2‐isopropenyl‐3‐phenyloxirane and styrene and its functionalization

The radical ring‐opening copolymerization of 2‐isopropenyl‐3‐phenyloxirane (1) with styrene (St) was examined to obtain the copolymer [copoly(1‐St)] with a vinyl ether moiety in the main chain. The copolymers were obtained in moderate yields by copolymerization in various feed ratios of 1 and St over 120 °C; the number‐average molecular weights (M_n) were estimated to be 1800–4200 by gel permeation chromatography analysis. The ratio of the vinyl ether and St units of copoly(1‐St) was estimated with the ¹H NMR spectra and varied from 1/7 to 1/14 according to the initial feed ratio of 1 and St. The haloalkoxylation of copoly(1‐St) with ethylene glycol in the presence of N‐chlorosuccinimide produced a new copolymer with alcohol groups and chlorine atoms in the side group in a high yield. The M_n value of the haloalkoxylated polymer was almost the same as that of the starting copoly(1‐St). The incorporated halogen was determined by elemental analysis. The analytical result indicated that over 88% of the vinyl ether groups participated in the haloalkoxylation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3729–3735, 2000     

Oxidative copolymerization of 2‐pyridylamine and aniline

A series of copolymers were easily synthesized via the chemical oxidative polymerization of 2‐pyridylamine (2PA) and aniline (AN) in an acidic aqueous medium. The yield, intrinsic viscosity, and solubility of the copolymers were studied through changes in the 2PA/AN molar ratio, polymerization temperature, oxidant, oxidant/monomer molar ratio, and polymerization medium. The resulting 2PA/AN copolymers were characterized by ¹H NMR, Fourier transform infrared, wide‐angle X‐ray diffraction, and thermogravimetric techniques. The results showed that the oxidative copolymerization from 2PA and AN was exothermic. The resultant copolymers were amorphous and exhibited enhanced solubility in comparison with polyaniline. The 2PA/AN copolymers showed the highest decomposition temperature (530 °C), the slowest maximum‐weight‐loss rate (1.2 %/min), the largest char yield (45 wt %), and the greatest degradation activation energy (65 kJ/mol) in nitrogen. The thermostability of the copolymers was generally higher in nitrogen than in air. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4407–4418, 2000     

Cyclopolymerization of α,ω‐heterodifunctional monomers containing styrene and maleimide moieties

A series of α,ω‐heterodifunctional monomers with styrene (St) and maleimide moieties bridged by a varied length of oligo‐ethylene glycol (OEG) linkers were synthesized. Cyclopolymerizations of these monomers through reversible addition–fragmentation chain transfer‐mediated alternating radical copolymerization between intramolecular St and maleimide moieties were investigated. For the monomers with three or more ethylene glycol (EG) units, their cyclopolymerizations can be realized properly in low monomer feeding concentrations, affording well‐defined cyclopolymers with crown ether encircled in their main chains. Importantly, the cyclopolymerizations of monomers with six or seven EG units in the presence of KPF₆ could be enhanced by the supramolecular effects between the OEG linkers and the potassium metal ion. Thus, the monomer feeding concentration could be largely improved, which may benefit preparation of the cyclopolymers with high degrees of copolymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 330–338     

A novel approach to the characterization of end groups in styrene–methyl methacrylate copolymers by pyrolysis–gas chromatography

The end groups of styrene–methyl methacrylate (St‐MMA) copolymers polymerized radically with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator, which are difficult to characterize even by NMR, were investigated by pyrolysis–gas chromatography. On the resulting pyrograms, characteristic products that formed from the end‐group moiety due to AIBN, such as 2‐cyanopropane, 2‐cyanopropen, and various compounds consisting of an isobutyronitrile group and a monomer unit, were observed together with those from the main chain, such as St and MMA monomers and various dimeric and trimeric products. The relative abundance between the recombination and disproportionation termination reactions in the copolymerization process was estimated from the relative intensities between the characteristic peaks of the end group and those of the main chain. Thus, the estimated abundance for the termination reactions suggested that the polymerization process for this particular copolymer system terminated preferentially by recombination rather than by disproportionation. Furthermore, the relative abundance between the monomer units adjacent to the chain‐end AIBN residues was estimated on the basis of the peak intensities of the products consisting of an isobutyronitrile group and either monomer unit, which reflected the penultimate neighboring structure of the end group in the polymer chain. Thus, the observed results suggested that the isobutyronitrile radical formed by the dissociation of AIBN in the initiation reaction was predominantly adjoined by St monomer rather than by MMA monomer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1880–1888, 2000     

Water‐soluble,thermoresponsive, hyperbranched copolymers based on PEG‐methacrylates: Synthesis,characterization, and LCST behavior

A series of water‐soluble thermoresponsive hyperbranched copoly(oligoethylene glycol)s were synthesized by copolymerization of di(ethylene glycol) methacrylate (DEG‐MA) and oligo(ethylene glycol) methacrylate (OEG‐MA, M_w = 475 g/mol), with ethylene glycol dimethacrylate (EGD‐MA) used as the crosslinker, via reversible addition fragmentation chain transfer polymerization. Polymers were characterized by size exclusion chromatography and nuclear magnetic resonance analyses. According to the monomer composition, that is, the ratio of OEG‐MA: DEG‐MA: EGD‐MA, the lower critical solution temperature (LCST) could be tuned from 25 °C to 90 °C. The thermoresponsive properties of these hyperbranched copolymers were studied carefully and compared with their linear analogs. It was found that molecular architecture influences thermoresponsive behavior, with a decrease of around 5–10 °C in the LCST of the hyperbranched polymers compared with the LCST of linear chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2783–2792, 2010     

Functional copolymer/organo‐MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA‐alt‐1‐octadecene)‐g‐PLA layered silicate nanocomposites with nanoporous core–shell morphology

Novel bioengineering functional copolymer‐g‐biopolymer‐based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L‐lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1‐octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo‐MMT clay (reactive ODA‐MMT and non‐reactive DMDA‐MMT) complexes as nanofillers and tin(oct)₂ as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT‐IR spectroscopy, X‐ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA‐DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro‐ and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H‐bonding and self‐organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride‐containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer‐g‐biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of lithium perchlorate on the spontaneous copolymerization of 4‐vinylpyridine with various electron‐rich vinyl monomers

The spontaneous copolymerization of 4‐vinylpyridine (4‐VP) activated with lithium perchlorate (LiClO₄) with various electron rich monomers (p‐methoxystyrene, MeOSt; p‐methylstyrene, MeSt; styrene, St) was investigated in various solvent systems at 75°C. Increasing the LiClO₄ concentration and the nucleophilicity of the electron rich monomer increased the copolymer yields. Both ¹H‐NMR and elemental analysis confirmed the almost 1:1 copolymer structure for VP/MeOSt system which possessed high molecular weight and narrow polydispersity (PDI). Compared to 4‐VP activated with zinc chloride, LiClO₄ systems showed slightly lower yields and much narrower PDI. We also investigated the spontaneous copolymerization of 4‐VP activated with various protic acids in the reaction with various electron rich comonomers. However, generally protic salt forms showed less solubility in organic solvents and showed low molecular weight polymer products with low yields. The proposed initiation mechanism exhibits the formation of a σ‐bond between the β‐carbons of the two donor‐acceptor monomers, creating the 1,4‐tetramethylene biradical intermediate initiating the copolymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1709–1716, 1999     

Atom transfer radical copolymerization of styrene and N‐cyclohexylmaleimide

Atom transfer radical copolymerization of Styrene (St) and N‐cyclohexylmaleimide (NCMI) with the CuBr/bipyridine catalyst in anisole, initiated by 1‐phenylethyl bromide (1‐PEBr) or tetra‐(bromomethyl)benzene (TBMB), afforded well‐defined copolymers with predetermined molecular weights and low polydispersities, M_w/M_n < 1.5. The influences of several factors, such as temperature, solvent, and monomer ratio, on the copolymerization with the CuBr/bpy catalyst system were subsequently investigated. The apparent enthalpy of activation for the overall copolymerization was measured to be 28.2 kJ/mol. The monomer reactivity ratios were evaluated to be r_NCMI = 0.046 and r_St = 0.127. Using TBMB as the initiator produced four‐armed star copolymer. The copolymerization of styrene and NCMI with TBMB/CuBr/bpy in PhOCH₃ at 110 °C was found to provide good control of molecular weights and polydispersities and the similar copolymerization in cyclohexanone displayed poor control. The glass transition temperature of the resultant copolymer increases with increasing f_NCMI, which indicates that the heat resistance of the copolymer has been improved by increasing NCMI. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1203–1209, 2000     

Novel amorphous perfluorocopolymeric system: Copolymers of perfluoro‐2‐methylene‐1,3‐dioxolane derivatives

Perfluorotetrahydro‐2‐methylene‐furo[3,4‐d][1,3]dioxole (monomer I ) and perfluoro‐2‐methylene‐4‐methoxymethyl‐1,3‐dioxolane (monomer II ) are soluble in perfluorinated or partially fluorinated solvents and readily polymerize in solution or in bulk when initiated by a free‐radical initiator, perfluorodibenzoyl peroxide. The copolymerization parameters have been determined with in situ ¹⁹F NMR measurements. The copolymerization reactivity ratios are r _I = 1.80 and r _II = 0.80 in 1,1,2‐trichlorotrifluoroethane at 41 °C and r _I = 0.97 and r _II = 0.85 for the bulk polymerization. These data show that this copolymerization pair has a good copolymerization tendency and yields nearly ideal random copolymers. The copolymers have only one glass‐transition temperature from 101 to 168 °C, depending on the copolymer compositions. Melting endotherms have not been observed in their differential scanning calorimetry traces, and this indicates that all the copolymers with different compositions are completely amorphous. These copolymers are thermally stable (the initial decomposition temperatures are higher than 350 °C under an N₂ atmosphere) and have low refractive indices and high optical transparency from UV to near‐infrared. Copolymer films prepared by casting were flexible and tough. These properties make the copolymers ideal candidates as optical and electrical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1613–1618, 2006     

Block copolymerization of tert‐butyl methacrylate with α,ω‐difunctionalized polystyrene macroiniferter and hydrolysis to amphiphilic block copolymer

The block copolymerization of tert‐butyl methacrylate (tBMA) with a difunctionalized polystyrene (PS) macroinitiator was investigated. The polymerizations were performed under UV light irradiation using PS bearing α‐ and ω‐functionalized end groups containing diethyldithiocarbamyl groups as a macroiniferter. Kinetic studies indicate the molecular weights of triblock copolymers increased linearly with the conversion. Block copolymers with different lengths of PtBMA segments were easily prepared by varying the ratio of tBMA and PS macroiniferter or by controlling the monomer conversion. The formations of block copolymers were characterized by gel permeation chromatographic, ¹H NMR, and DSC analyses. PtBMA segments of the triblock copolymer were subsequently hydrolyzed quantitatively to poly(methacrylic acid) segments using concentrated HCl as a catalyst in a refluxing solution of dioxane, and then an amphiphilic ABA triblock copolymer was produced. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1450–1455, 2001     

Nanocomposites of vinyl chloride–acrylonitrile copolymer and silica

Vinyl chloride–acrylonitrile (VC–AN) copolymer was synthesized through emulsion copolymerization. VC–AN copolymer/silica nanocomposites were prepared by solution blending of copolymer and silica in a common solvent, N,N‐dimethylformamide (DMF). The rheology studies show that the shear‐thinning behavior of the VC–AN copolymer solution becomes less distinct as nano particles are introduced. It was also found that the viscosity of the copolymer solution decreases with adding small amount of nano particles. Transmission electron microscopy observations indicate that the UV‐treated silica could disperse well in the copolymer matrix. Differential scanning calorimeter studies suggest that the presence of the silica suppresses crystallization of the AN segments in the copolymers. Because of the interactions between copolymer chains and inorganic particles, the thermal stability and mechanical strength of the VC–AN copolymers are improved considerably. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3127–3134, 2005