Cationic Grafting of Vinyl Polymers onto a Carbon Whisker,Initiated by Acylium Perchlorate Groups Introduced onto the Surface

Abstract

The cationic graft polymerization of vinyl monomers onto a carbon whisker, vapor-grown carbon fiber, initiated by acylium perchlorate groups introduced onto the surface, was investigated. The introduction of acylium perchlorate groups onto a carbon whisker was achieved by the treatment of a carbon whisker having acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride, with silver perchlorate in nitrobenzene. It was found that the cationic polymerization of vinyl monomers, such as styrene, indene, N-vinyl-2-pyrrolidone, and n-butyl vinyl ether, is initiated by acylium perchlorate groups on a carbon whisker. In the polymerization, the corresponding vinyl polymers were grafted onto a carbon-whisker surface based on the propagation of polymer from the surface: the percentage of grafting of polystyrene and polyindene reached 42.5 and 100.3%, respectively. The percentage of polystyrene grafting decreased with increasing polymerization temperature because of preferential chain transfer reactions at higher temperatures. Polymer-grafted carbon whisker gave a stable colloidal dispersion in a good solvent for grafted polymer.     

Grafting of polyesters onto carbon black. VI. Copolymerization of alkylene carbonate with cyclic acid anhydride initiated by alkali metal carboxylate groups on carbon black surface

The ring-opening copolymerization of alkylene carbonate with cyclic acid anhydride was found to be initiated by carbon black containing potassium carboxylate (COOK) groups to give an alternating polymer, i.e., polyester. The polyester was propagated from COOK groups and effectively grafted from carbon black surface: e.g., the grafting ratio of polyester from ethylene carbonate (EC) and phthalic anhydride (PAn) went up to over 100%. On the other hand, the initiating activity of alkali metal carboxylate groups increased, depending on the alkali metal countercation, in the following order: COOLi < COONa < COOK < COORb < COOCs. This order was in agreement with that of increasing electropositivity of the counteraction. The activation energy of the copolymerization of EC with PAn was determined to be 26.3 kcal/mol. The rate of the copolymerization was accelerated in an aprotic solvent such as N-methyl-2-pyrrolidone. Furthermore, the effect of solvent and polymerization temperature on the grafting ratio of polyester was investigated.     

Grafting of polymers onto carbon whisker by anionic graft polymerization of vinyl monomers using metallized aromatic rings and/or phenoxy lithium groups on the surface as initiator

During the anionic polymerization of methyl methacrylate (MMA) initiated by n-butyl-lithium (n-BuLi) in the presence of carbon whisker, PMMA was found to be grafted onto the surface depending on the propagation from OLi groups, which are produced by the reaction of oxygen containing groups on the surface with n-BuLi. But no grafting of polystyrene was observed at all. By the activation of OLi groups by the addition of crown ether, however, the grafting of polystyrene onto the carbon whisker was achieved. On the other hand, it was found that metallized carbon whisker also initiates the anionic graft polymerization of MMA and styrene: percentage of grafting of PMMA and polystyrene reached 231.3 and 157.9%, respectively. The metalation of carbon whisker was achieved by the treatment with n-BuLi in aprotic polar solvents, such as N,N,N′,N′-tetramethylethylene-diamine or hexamethylphosphorous triamide, and in toluene in the presence of complexing agent of cation such as crown ether or a small amount of aprotic solvent. In the polymerization, grafted polymer chains were considered to propagate both from metallized aromatic rings and from OLi groups. The polymer-grafted carbon whisker gave a stable colloidal dispersion in organic solvents.     

Grafting polyesters onto carbon black. I. Polymerization of β-propiolactone initiated by alkali metal carboxylate group on the surface of carbon black

By use of carbon black that contained alkali metal carboxylate (? COOM; M?Li, Na, K, Rb, or Cs) group as catalyst the anionic polymerization of β-propiolactone (PL) was carried out at 50°C and the grafting of polyester onto the carbon black surface was investigated. Carbon black that contained ? COOM group was prepared by the reaction of carboxyl group on the surface with corresponding alkali metal hydroxide and was able to initiate the anionic ring-opening polymerization of PL. The carbon black obtained from the reaction gave a stable colloidal dispersion in an organic solvent. It was confirmed that the polyester formed was grafted effectively onto the surface; for instance, by using carbon black that contained ? COOK group as catalyst the grafting ratio was increased to 145% (viz., 1.45 g of polyester was grafted/1 g of carbon black) with an increase in conversion. Furthermore, the effect of alkali metal countercation (M⁺) on the polymerization was studied. The initiating activity of ? COOM group on the surface increased in the following order: ? COOLi < ? COONa < ? COOK < ? COORb < ? COOCs. This order was in agreement with that of increasing electropositivity of these alkali metals.     

Radical Graft Polymerization of Vinyl Monomers Initiated by A20 Groups Introduced Onto a Carbon Black Surface: Effect of azo Groups on Graft Polymerization

The radical graft polymerization of vinyl monomers from carbon black initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto carbon black surface was achieved by three methods: the reaction of 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP) with (1) epoxide groups, which were introduced by the reaction of carbon black with chlorometh-yloxirane; (2) acyl chloride groups, which were introduced by the reaction of carboxyl groups on the surface with thionyl chloride; and (3) 3-chloroformyl-1-cyano-1-methylpropyl groups, which were introduced by the reaction of carbon black with 4,4′-azobis(4-cyanovaleric acid) and then thionyl chloride. The amount of azo groups introduced onto the surface by the above methods was determined to be 0.07-0.19 mmol/g. The graft polymerization of methyl methacrylate was found to be initiated by azo groups introduced onto the carbon black surface. During the polymerization, poly(methyl methacrylate) was effectively grafted onto carbon black through propagation of the polymer from the radical produced on the surface by the decomposition of the azo groups. The percentage of grafting using carbon black having azo groups introduced by method 1 increased to 40%. It was also found that the graft polymerization of several vinyl monomers such as styrene, acrylonitrile, and acrylic acid was initiated by the azo groups introduced onto the surface and the corresponding polymer was effectively grafted onto the surface. Furthermore, the effect of the amount of carbon black having azo groups on the graft polymerization was investigated.     

Photografting of polymers onto nanosized silica surface initiated by eosin moieties immobilized onto the surface

The photograft polymerization of various vinyl monomers onto nanosized silica surfaces was investigated. It was initiated by eosin moieties introduced onto the silica surface. The preparation of the silica with eosin moieties was achieved by the reaction of eosin with benzyl chloride groups on the silica surface.These were introduced by the reaction of surface silanol groups with 4‐(chloromethyl)phenyltrimethoxysilane in the presence of t‐butyl ammonium bromide as a phase‐transfer catalyst. The photopolymerization of various vinyl monomers, such as styrene, acrylamide, acrylic acid, and acrylonitrile was successfully initiated by eosin moieties on the silica surface in the presence of ascorbic acid as a reducing agent and by oxygen. The corresponding polymers were grafted from the silica surface. The grafting efficiency (percentage of grafted polymer to total polymer formed) in the photoinitiation system was much larger than that in the radical polymerization initiated by surface radicals; these radicals were formed by the thermal decomposition of azo groups introduced onto the silica surface. It was found that the polymer‐grafted silica gave stable dispersions in good solvents of grafted polymer and the wettability of the surfaces can be easily controlled by grafting of polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 600–606, 2005     

Heat-Resistant Polymer-Grafted Carbon Black: Grafting of Poly(Organophosphazenes) onto Carbon Black Surface

Abstract

The grafting of poly(organophosphazenes) onto carbon black surface by the reaction of poly(dichlorophosphazene) (PDCP) with carbon black having sodium phenoxide groups was investigated. PDCP was prepared by the ring-opening polymerization of hexachlorocyclotriphos-phazene in solution using sulfamic acid as a catalyst. The introduction of sodium phenoxide groups onto carbon black was achieved by treatment of phenolic hydroxyl groups on the surface with sodium hydroxide in methanol. Poly(diphenoxyphosphazene) (PDPP) was successfully grafted onto carbon black by the reaction of PDCP with sodium phenoxide groups introduced onto the surface followed by the replacement of chlorine atoms in PDCP with phenoxy groups. The percentage of grafting onto carbon black increased to 206% at 30°C after 12 h. It was found that only 1.4% of sodium phenoxide groups on carbon black surface was used for the grafting of PDCP because of the blocking of the surface by grafted polymer chains. Poly(diaminophenylphosphazene) and poly-(diethoxyphosphazene) were also grafted onto carbon black surface by the treatment of PDCP-grafted carbon black with aniline and sodium ethoxide, respectively. Poly(organophosphazenes)-grafted carbon blacks produced stable colloidal dispersions in good solvents for grafted polymers. Furthermore, thermogravimetric analysis indicated that poly-(organophosphazenes)-grafted carbon blacks were stable in air about 300°C.     

Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

The effective grafting of vinyl polymers onto an ultrafine silica surface was successfully achieved by the photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface with Mn₂(CO)₁₀ under UV irradiation at 25 °C. The introduction of trichloroacetyl groups onto the surface of silica was achieved by the reaction of trichloroacetyl isocyanate with surface amino groups, which were introduced by the treatment of silica with 3‐aminopropyltriethoxysilane. During the polymerization, the corresponding polymers were effectively grafted onto the surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mn₂(CO)₁₀. The percentage of poly(methyl methacrylate) grafting onto the silica reached 714.6% after 90 min. The grafting efficiency (proportion of grafted polymer to total polymer formed) in the polymerization of methyl methacrylate was very high, about 80%, indicating the depression of formation of ungrafted polymer. Polymer‐grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2157–2163, 2001     

Graft Polymerization of Vinyl Monomers Onto Carbon Black by Use of the Redox System Consisting of Ceric Ions and Carbon Black Carrying Alcoholic Hydroxyl Groups

The radical graft polymerization of vinyl monomers onto carbon black initiated by a redox system consisting of ceric ion and carbon black having alcoholic hydroxyl groups was investigated. The introduction of alcoholic hydroxyl groups onto the carbon black surface was achieved by the reaction of carbon black with alcoholic hydroxyl radicals, formed by the reaction of alcohol with benzoyl peroxide. The rate of the polymerization of acrylamide (AAm) initiated by the redox system was found to increase in the following order of hydroxyl groups: 1-hydroxyoctyl < 1-hydroxypropyl < 1-hydroxyethyl < hydroxymethyl < 1-hydroxy-1-methylethyl. In the redox polymerization, poly-AAm was effectively grafted onto carbon black by propagation of the polymer from the radical formed by the reaction of ceric ions with the alcoholic hydroxy groups. The percentage of grafting increased with increasing conversion. By use of this redox system, poly(acrylic acid), polyacrylonitrile, and poly(N-vinyl-2-pyrrolidone) could be grafted onto carbon black, but poly(methyl methacrylate) and polystyrene could not be so grafted. The graft polymerization of AAm by use of a redox system consisting of ceric ion and PVA-grafted carbon black was also investigated.     

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerization of vinyl monomers from glass fiber surface initiated by alkylazo groups introduced onto the fiber surface. The introduction of azo groups onto the glass fiber surface was achieved by reaction of isocyanate groups which were previously attached onto the surface with two kinds of azo initiators, 4,4′-azobis(4-cyanopentanoic acid) (ACPA) and 2,2′-azobis(2-cyanopropanol) (ACP). The amounts of surface azo groups introduced by ACPA and ACP were both determined to be 1.3 × 10⁻⁵ mol g⁻¹ by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was found to be initiated in the presence of the glass fiber having surface azo groups. During the polymerization, part of resultant poly(MMA) grafted onto the fiber surface through propagation of the polymer from the surface radicals produced by the decomposition of the azo groups. The percentage of grafting of poly(MMA) reached 48.1% after 24 h. The graft polymerizations of other monomers, such as styrene, N-vinylcarbazole, and acrylic acid, were also initiated by the surface azo groups, and the corresponding polymer effectively grafted onto the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2121–2128, 1999     

Graft polymerization of methyl methacrylate from silica initiated by peroxide groups introduced onto the surface

The surface grafting onto ultrafine silica by the radical polymerization of methyl methacrylate (MMA) initiated by peroxide groups introduced onto the surface was investigated. The introduction of peroxide groups onto the silica surface was achieved by the reaction of hydrogen peroxide with chlorosilyl groups, which were introduced by the treatment of silica with thionyl chloride. The content of diisopropylbenzene peroxide and tert-butyl peroxide groups introduced onto the silica according to the above method was determined to be 0.11 and 0.08 mmol/g, respectively. It was found that the polymerization of MMA is initiated by silica having these peroxide groups. In the polymerization, polyMMA was grafted onto silica surface: the percentage of grafting reached about 70%. Therefore, it was concluded that the polymerization of MMA is initiated by surface radicals formed by the decomposition of peroxide groups on silica and polyMMA is grafted through the propagation from the surface. During the polymerization, ungrafted polyMMA was also formed because of the formation of initiator fragments by the decomposition of peroxide groups: the grafting efficiency of the graft polymerization was 30–40%. PolyMMA-grafted silica produced a stable colloidal dispersion in organic solvents for polyMMA. © 1992 John Wiley & Sons, Inc.     

Effect of polymerization conditions on the molecular weight of polystyrene grafted onto silica in the radical graft polymerization initiated by azo or peroxyester groups introduced onto the surface

The effect of polymerization conditions on the molecular weight of polystyrene grafted onto silica obtained from the radical graft polymerization initiated by azo and peroxyester groups introduced onto the surface was investigated. The molecular weight of polystyrene grafted onto silica obtained from the radical graft polymerization initiated by surface azo and peroxyester groups decreased with decreasing monomer concentration and polymerization temperature. The molecular weight of polystyrene was found to be controlled to some extent by the addition of a chain transfer agent. The molecular weight of grafted chain on silica surface obtained from the graft polymerization initiated by surface radicals formed by photodecomposition of azo groups was considerably smaller than that by thermal decomposition. The number of grafted polystyrene in photopolymeriztion, however, was much larger than that in thermal polymerization. These results are explained by the blocking of surface radicals formed on the silica surface by previously grafted polymer chain: when the decomposition of surface azo and peroxyester groups proceed instantaneously at the initial stage of the polymerization, the number of grafted polymer chains increased.     

Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of γ‐ray‐irradiated silica

The effects of radicals on silica surface, which were formed by γ‐ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of γ‐ray‐irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of γ‐ray‐irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of γ‐ray‐irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC‐MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical (“grafting from” mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals (“grafting onto” mechanism) proceeded to give relatively higher molecular weight polymer‐grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972–2979, 2006     

Polymerization of vinyl monomers in the presence of silica having surface functional groups

The surface of silica was modified by mercaptopropyl, chloropropyl, aminopropyl, and methacryloxypropyl groups by the treatment of silica with the corresponding silane coupling agents, and the effects of functional groups on the surface on the polymerization of vinyl monomers initiated by benzoyl peroxide or 2,2-azobisisobutyronitrile were investigated. Although the rate of the polymerization of vinyl monomers in the presence of silica was almost equal to that in the absence of silica, a part of polymer formed was grafted onto silica surface. The polymerization was considerably retarded in the presence of these functionalized silicas and the corresponding polymers were effectively grafted onto the surface. The molecular weight of ungrafted polymer formed in the presence of the functionalized silica was lower than that formed in the presence of unmodified silica. This indicates that the chain transfer reaction of growing polymer radical to functionalized silica surface forms radicals on the surface, which then couples with growing polymer radical and/or reinitiates the polymerization to give rise to the grafting of polymers onto the surface. In the case of silica having methacryloxypropyl groups, the grafting based on the copolymerization of vinyl monomer with the surface methacryloxypropyl groups was considered to successfully proceed.     

Photografting of vinyl polymers onto ultrafine inorganic particles: Photopolymerization of vinyl monomers initiated by AZO groups introduced onto these surfaces

The photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain. © 1994 John Wiley & Sons, Inc.     

Grafting of polymers with controlled molecular weight onto ultrafine silica surface

To graft polymers with controlled molecular weight and narrow molecular weight distribution, the grafting of polymers onto ultrafine silica surface by the termination of living polymer cation with amino groups introduced onto the surface was investigated. The introduction of amino or N-phenylamino groups onto the silica surface was achieved by the treatment of silica with γ-aminopropyltriethxysilane or N-phenyl-γ-aminopropyltrimethoxysilane. It was found that these amino groups on silica are readily reacted with living poly(isobutyl vinyl ether) (polyIBVE), which was generated with CF₃COOH/ZnCl₂ initiating system, and polyIBVE with controlled molecular weight and narrow molecular weight distribution is grafted onto the surface. By the termination of living poly(2-methyl-2-oxazoline), which was generated with methyl p-toluenesulfonate initiator, with amino groups on silica, polyMeOZO was also grafted onto the surface. The percentage of grafting of polymer onto the silica surface decreased with increasing molecular weight of the living polymer, because the steric hindrance of silica surface increases with increasing molecular weight of living polymer. Polymer-grafted silica gave a stable dispersion in a good solvent for grafted chains. © 1995 John Wiley & Sons, Inc.     

Effect of rate retardation in RAFT grafting polymerization from silicon wafer surface

Polystyrene and poly(butyl acrylate) were grafted from silicon wafer surface by reversible addition‐fragmentation chain transfer (RAFT) polymerization. Three RAFT agents were immobilized onto silicon wafer through their leaving/initiating groups (R group). Grafting polymerization of butyl acrylate (BA) and styrene (St) was then carried out from the immobilized RAFT agents. The immobilization of the RAFT agents and the subsequent grafting polymerization of St and BA were evaluated by ellipsometry and X‐ray photoelectron spectroscopy. It was found that type of monomer, structure of RAFT agent, and local RAFT concentration on the surface have dramatic influences on the thickness of grafted polymer layer. The grafting polymerization with more severe rate retardation effect yielded thinner polymer films on the silicon wafer. Selection of a RAFT agent with little rate retardation was critical in the grafting polymerization to achieve thick films. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 970–978, 2008     

Grafting of hyperbranched cyclotriphosphazene polymer onto silica nanoparticle and carbon black surfaces

The surface grafting of hyperbranched cyclotriphosphazene polymer onto silica nanoparticles and carbon black was investigated. The grafting of hyperbranched cyclotriphosphazene polymer onto these surfaces was achieved by the repeated reactions of hexachlorocyclotriphosphazene with hexamethylenediamine from surface amino groups and sodium carboxylate groups, respectively. The percentage of grafting onto silica and carbon black surfaces exceeded 760 and 390%, respectively. However, it proved difficult to achieve the theoretical growth of cyclotriphosphazene polymer from these surfaces because of steric hindrance. The introduction of sulfonic acid groups was successfully achieved by the reaction of terminal chlorophosphazene groups of the hyperbranched polymer‐grafted silica and carbon black with sulfanilic acid. The content of sulfonic acid groups introduced onto silica and carbon black surfaces was 4.98 mmol/g and 5.70 mmol/g, respectively. The sulfonated cyclotriphosphazene polymer‐grafted carbon black was extremely hydrophilic, yielding stable colloidal dispersions in polar solvents. The sulfonated cyclotriphosphazene polymer‐grafted silica and carbon black showed ionic conductivity, with the conductance increasing exponentially with increasing relative humidity and temperature. This study may offer important leads in the application of silica nanoparticles and carbon black in polymeric membranes for fuel cells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4218–4226, 2008     

SURFACE GRAFTING OF POLYESTERS ONTO ORGANIC PIGMENTS AND THEIR DISPERSIBILITY IN ORGANIC SOLVENT

To modify the dispersibility of an organic pigment, such as quinacridone and anthraquinone, in organic solvents, the surface grafting of polyesters onto organic pigments by the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate (COOK) groups introduced onto these surfaces was investigated. The organic pigment having COOK groups was prepared by the following two methods: (a) the reaction of potassium carbonate with surface acyl chloride groups, which were introduced by the treatment of surface amino groups with adipoyl dich bride, and (b) the graft polymerization of potassium acrylate initiated by azo groups introduced onto the surface. The anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was initiated by COOK groups introduced onto the organic pigment surfaces to give the corresponding polyester-grafted organic pigments. The dispersibility of organic pigments in organic solvent was remarkably improved by the grafting of polyesters onto the surface.     

Radical graft polymerization of vinyl monomers onto nanoparticles in ionic liquid initiated by azo groups introduced onto the surface

The radical graft polymerization of vinyl monomers, such as styrene and methyl methacrylate, initiated by azo groups introduced onto silica nanoparticle and carbon black surfaces in room temperature ionic liquid (IL) were investigated. In this work, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) was used as IL. The percentage of polystyrene and poly(methyl methacrylate) grafting onto silica nanoparticle and carbon black increased with increasing reaction time. The percentage of grafting in IL was much larger than that in 1,4‐dioxane. The molecular weight of polystyrene grafted onto the silica surface in IL was almost equal to that in 1,4‐dioxane. The result indicates that the amount of grafted polystyrene in IL is five times that in 1,4‐dioxane. This may be due to the fact that lifetime of the surface radical formed by the group of azo is prolonged because of high viscosity of IL. Therefore, the surface azo groups were effectively used as initiating sites for the graft polymerization. In addition, the reduction of waste solvent was achieved by use of IL as reaction solvent, because unreacted monomer could be removed under vacuum after the reaction and the reuse of IL was easily achieved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1143–1149, 2007