Seeded semibatch emulsion polymerization of butyl acrylate: Effect of the chain‐transfer agent on the kinetics and structural properties

The effect of dodecane‐1‐thiol on the kinetics, gel fraction, level of branches, and sol molecular weight distribution of the seeded semibatch emulsion polymerization of n‐butyl acrylate carried out at 75 °C was investigated. The gel fraction was strongly affected by the content of the chain‐transfer agent (CTA). The sol weight‐average molecular weights decreased with increasing CTA concentration, whereas no effect on the kinetics and the level of branches was observed. The experimental data were analyzed with a mathematical model of the process that was able to catch fairly well the effect of the process variable. In addition, adhesive tests were carried out to check the effect of the gel fraction on the adhesive properties. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1106–1119, 2001     

Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short‐chain alcohols

Styrene microemulsion polymerizations with different short‐chain alcohols [n‐C_iH_2i+1OH (C_iOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50–70 °C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C₆OH > C₄OH > C₅OH. This was related to the differences in the water solubility of C_iOH and the structure of the oil–water interface. The feasibility of using a water‐insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (C_iOH), the SPS concentration, and the initiator type (oil‐soluble 2,2′‐azobisisobutyronitrile versus water‐soluble SPS). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199–3210, 2001     

Titanium‐mediated living radical styrene polymerizations. VI. Cp2TiCl‐catalyzed initiation by epoxide radical ring opening: Effect of the reducing agents,temperature, and titanium/epoxide and titanium/zinc ratios

The effects of the reducing agent, temperature, and epoxide/Ti and Ti/Zn ratios were investigated for the Cp₂TiCl‐catalyzed living radical polymerization of styrene initiated by epoxide radical ring opening. No reduction of bis(cyclopentadienyl)titanium dichloride occurred with Cu, Devarda's alloy, Ni, Ce, Cr, Sn, Mo, and ascorbic acid, whereas Al, lithium nitride, Mn, Sm, and Fe led to free‐radical or poorly controlled polymerizations. The best results were obtained with Zn alloy, powder, or nanoparticles. Nano‐Zn provided the lowest polydispersity index values, highest initiator efficiency (IE), and fastest reaction rate while maintaining a well‐defined living polymerization. Progressively lower polydispersity was obtained with an increasing excess of Zn with an optimum at Cp₂TiCl/Zn = 1/2. This was rationalized through the heterogeneous nature of Zn and its possible involvement in the reversible termination step. The polymerization was insensitive to light or dark conditions, and a linear dependence of M_n on the conversion was observed at all temperatures in the 60–130 °C range with an optimum at 70–90 °C. A stoichiometric 1/2 epoxide/Ti ratio provided low polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.2) and high IE, whereas increasing the epoxide/Ti ratio to 1/3 maintained a low polydispersity index but decreased the IE. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2156–2165, 2006     

Ring‐opening polymerization of the cyclic dimer of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) (PTT) was prepared by the ring‐opening polymerization of its cyclic dimer. Antimony(III) oxide, titanium(IV) butoxide, dibutyltin oxide, and titanium(IV) isopropoxide were used as catalysts. Among the catalysts, titanium(IV) butoxide was the most effective for the same reaction conditions. A weight‐average molecular weight of 63,500 g/mol was obtained from ring‐opening poly merization at 265 °C for 2 h in the presence of 0.5 mol % titanium(IV) butoxide. The PTTs obtained from the polymerization catalyzed with increasing amounts of antimony(III) oxide showed increasing weight‐average molecular weights and reaction conversions. When 1 mol % antimony(III) oxide was used, the weight‐average molecular weight was 32,000 g/mol and the conversion was 82% after 1 h of polymerization at 265 °C. In the case of the polymer catalyzed by titanium(IV) butoxide under the same conditions, the weight‐average molecular weight and conversion were 40,000 g/mol and 77% when 0.25 mol % was used, whereas 0.5 mol % catalyst produced a weight‐average molecular weight of 27,000 g/mol and a conversion of 95%. To get an acceptable molecular weight and relatively high reaction conversion, a catalyst concentration of at least 0.5 mol % was found to be necessary, in contrast to conventional condensation polymerizations, which require only about one‐tenth of this amount of the catalyst. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6801–6809, 2006     

Reversible addition–fragmentation chain transfer polymerization of methyl methacrylate in suspension

The reversible addition–fragmentation chain transfer polymerization of methyl methacrylate mediated by 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) in bulk (60 and 70 °C) and suspension (70 °C) was studied, and in both polymerization systems, a good control of the molecular weight and polydispersity was observed. Stable suspension polymerizations were carried out over a range of CPDB concentrations, and with increasing CPDB concentration, the particle size and polydispersity index of the produced polymer decreased. The former was ascribed to the lower viscosities of the monomer and polymer droplets at low conversions, which caused easier breakup with the applied shear stresses. Lower polydispersity indices at higher CPDB concentrations were probably caused by a diminished gel effect, which was observed at lower CPDB concentrations at high conversions, causing a broadening of the molecular weight distribution. The livingness of the polymers formed in suspension was proven by successful chain extensions with methyl methacrylate, styrene, and 2‐hydroxyethyl methacrylate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2001–2012, 2005     

Synthesis of poly(D,L‐lactic acid‐alt‐glycolic acid) from D,L‐3‐methylglycolide

D ,L ‐3‐Methylglycolide (MG) was synthesized via two step reactions with a good yield (42%). It was successfully polymerized in bulk with stannous octoate as a catalyst at 110 °C. The effects of the polymerization time and catalyst concentration on the molecular weight and monomer conversion were studied. Poly(D ,L ‐lactic acid‐co‐glycolic acid) (D ,L ‐PLGA50; 50/50 mol/mol) copolymers were successfully synthesized from the homopolymerization of MG with high polymerization rates and high monomer conversions under moderate polymerization conditions. ¹H NMR spectroscopy indicated that the bulk ring‐opening polymerization of MG conformed to the coordination–insertion mechanism. ¹³C NMR spectra of D ,L ‐PLGA50 copolymers obtained under different experimental conditions revealed that the copolymers had alternating structures of lactyl and glycolyl. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4179–4184, 2000     

Isoprene polymerization via reversible addition fragmentation chain transfer polymerization

Until recently, the primary living radical polymerization method available for preparing polyisoprene was nitroxide‐mediated radical polymerization, with reversible addition‐fragmentation chain transfer polymerization being applied only in a few cases within the last couple of years. We report here the preparation of polyisoprene by RAFT in the presence of the trithiocarbonate transfer agent S‐1‐dodecyl‐S′‐(r,r′‐dimethyl‐r′′‐acetic acid)trithiocarbonate and t‐butyl peroxide as the radical initiator. The kinetics of this polymerization at an optimized temperature of 125 °C and radical initiator concentration of 0.2 equiv relative to transfer agent have been studied in triplicate and demonstrate the living nature of the polymerization. These conditions resulted in polymers with narrow polydispersity indices, on the order of 1.2, with monomer conversions up to 30%. Retention of chain‐end functionality was demonstrated by polymerizing styrene as a second block from a polyisoprene macrotransfer agent, resulting in a block copolymer presenting a unimodal gel permeation chromatogram, and narrow molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4100–4108, 2007     

Kinetics of the microemulsion polymerization of styrene with short‐chain alcohols as the cosurfactant

The kinetics of styrene microemulsion polymerization stabilized by sodium dodecyl sulfate (SDS) and a series of short‐chain alcohols (n‐C_iH_2i+1OH, abbreviated as C_iOH, where i = 4, 5, or 6) at 60 °C was investigated. Sodium persulfate was used as the initiator. The microemulsion polymerization process can be divided into two intervals: the polymerization rate (R_p) first increases to a maximum at about a 20% conversion (interval I) and thereafter continues to decrease toward the end of the polymerization (interval II). For all the SDS/C_iOH‐stabilized polymerization systems, R_p increases when the initiator or monomer concentration increases. The average number of free radicals per particle is smaller than 0.5. The molecular weight of the polymer produced is primarily controlled by the chain‐transfer reaction. In general, the reaction kinetics for the polymerization system with C₄OH as the cosurfactant behaves quite differently from the kinetics of the C₅OH and C₆OH counterparts. This is closely related to the different water solubilities of these short‐chain alcohols and the different concentrations of the cosurfactants used in the preparation of the microemulsion. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 898–912, 2001     

Controlled free‐radical polymerization of 2‐vinylpyridine in the presence of nitroxides

Bulk free‐radical polymerization of 2‐vinylpyridine (2VP) in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) was studied under different conditions (temperature and presence of additives). Linear poly‐(2‐vinylpyridine) with a narrow molecular weight distribution and controllable molecular weight was prepared in the presence of acetic anhydride at 95 °C up to a conversion of 66%. At higher conversions side reactions became very important (pseudoliving polymerization). By applying this procedure, well‐defined random copolymers of 2VP with styrene or tert‐butylmethacrylate as well as block copolymers of 2VP with styrene were synthesized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2889–2895, 2001     

Visible‐light induced RAFT polymerization of styrenic monomers with aromatic aldehydes as organophotoredox catalysts

A photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization of p‐methylstyrene (p‐MS) and styrene (St) with 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid as the chain transfer agent (CTA) and aromatic aldehydes, including 4‐cyanobenzaldehyde (PC1), 2,4‐dimethoxy benzaldehyde, and 4‐methoxy benzaldehyde, as organic photocatalysts has been demonstrated via irradiation with 23 W compact fluorescent lamps. The kinetics of the polymerizations shows first order with respect to monomer conversions. Linear evolution of the M_n of the produced polymers with the monomer conversion is observed. Meanwhile, the as‐prepared polymers are of relatively narrow polydispersity (PDI = M_w/M_n). For instance, the polymerization of p‐MS shows living polymerization features using PC1 within a range of solvents. Especially, the M_n of PpMS increased from about 2100 to 12,700 g/mol with the monomer conversion from 8% to 52% in tetrahydrofuran. The controlled polymerization of St is also observed under optimal reaction conditions. However, the M_n discrepancy between the experimental readings and theoretical calculations is greater at the monomer conversions greater than 40% and the PDI increased gradually over the monomer conversion. This is probably because that CTA is strongly sensitive to the light irradiation with wave range around its characteristic absorption wavelength, leading to significant decomposition of CTA moieties during the RAFT polymerization. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2072–2079     

Lipase‐catalyzed ring‐opening polymerization of 6(S)‐methyl‐morpholine‐2,5‐dione

Lipase‐catalyzed ring‐opening bulk polymerizations of 6(S)‐methyl‐morpholine‐2,5‐dione (MMD) were investigated. Selected commercial lipases were screened as catalysts for MMD polymerization at 100 °C. Polymerizations catalyzed with 10 wt % porcine pancreatic lipase type II crude (PPL), lipase from Pseudomonas cepacia, and lipase type VII from Candida rugosa resulted in MMD conversions of about 75% in 3 days and in molecular weights ranging from 8200 to 12,100. Poly(6‐methyl‐morpholine‐2,5‐dione) [poly(MMD)] had a carboxylic acid group at one end and a hydroxyl group at the other end. However, lipase from Mucor javanicus showed lower catalytic activity for the polymerization. During the polymerization, racemization of the lactate residue took place. PPL was selected for further studies. The rate of polymerization increased with increasing PPL concentration under otherwise identical conditions. When the PPL concentration was 5 or 10 wt % with respect to MMD, a conversion of about 70% was reached after 6 days or 1 day, respectively, whereas for a PPL concentration of 1 wt %, the conversion was less than 20% even after 6 days. High concentrations of PPL (10 wt %) resulted in high number‐average molecular weights (<3 days); with a lower concentration of PPL, lower molecular weight poly(MMD) was obtained. The concentration of water was an important factor that controlled not only the conversion but also the molecular weight. With increasing water content, enhanced polymerization rates were achieved, whereas the molecular weight of poly(MMD) decreased. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3030–3039, 2005     

Alkylamines‐intercalated α‐zirconium phosphate as latent thermal anionic initiators

The reaction of glycidyl phenyl ether (GPE) with 1‐aminoalkanes‐intercalated α‐zirconium phosphate (α‐ZrP·1‐aminoalkane): 1‐aminoalkanes 1‐aminopropane (α‐ZrP·Pr), 1‐aminobutane (α‐ZrP·Bu), 1‐aminooctane (α‐ZrP·Oct), and 1‐aminohexadecane (α‐ZrP·Hed) was carried out at varying temperatures for 1 h periods. Reaction progress was not observed until the reactants were heated to 80 °C or above. On increasing the temperature, the conversion factors increased such that, at 140 °C, conversions of 62% (α‐ZrP·Pr), 60% (α‐ZrP·Bu), 67% (α‐ZrP·Oct), and 64% (α‐ZrP·Hed) were obtained. The thermal stabilities as latent initiators were tested: GPEs reacted with α‐ZrP·Pr, α‐ZrP·Bu, and α‐ZrP·Oct at 40 °C for 360 h achieved conversions of 83, 55, and 59%, respectively. In contrast, the reaction in the presence of α‐ZrP·Hed did not proceed at 40 °C. The order of the thermal stability of GPE in the presence of α‐ZrP·1‐aminoalkane intercalation compounds was: α‐ZrP·Hed > α‐ZrP·Bu ≈ α‐ZrP·Oct > α‐ZrP·Pr. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1854–1861     

Reversible addition–fragmentation chain transfer polymerization of glycidyl methacrylate with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate as a chain‐transfer agent

A reversible addition–fragmentation chain transfer (RAFT) agent, 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN), was synthesized and applied to the RAFT polymerization of glycidyl methacrylate (GMA). The polymerization was conducted both in bulk and in a solvent with 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at various temperatures. The results for both types of polymerizations showed that GMA could be polymerized in a controlled way by RAFT polymerization with CPDN as a RAFT agent; the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with the monomer conversion up to 96.7% at 60 °C, up to 98.9% at 80 °C in bulk, and up to 64.3% at 60 °C in a benzene solution. The polymerization rate of GMA in bulk was obviously faster than that in a benzene solution. The molecular weights obtained from gel permeation chromatography were close to the theoretical values, and the polydispersities of the polymer were relatively low up to high conversions in all cases. It was confirmed by a chain‐extension reaction that the AIBN‐initiated polymerizations of GMA with CPDN as a RAFT agent were well controlled and were consistent with the RAFT mechanism. The epoxy group remained intact in the polymers after the RAFT polymerization of GMA, as indicated by the ¹H NMR spectrum. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2558–2565, 2004     

Biodegradable hyperbranched polyesters derived from 1,1,1‐tris(hydroxymethyl)ethane

Low molar mass hyperbranched polyesters were prepared by polycondensation of 1,1,1‐tris(hydroxymethyl)ethane and various dimethyl esters of aliphatic dicarboxylic acids in bulk. The usefulness of nontoxic bismuth salts as transesterification catalysts for these polycondensations was studied. The maximum conversion increased, and the reaction time decreased in the following sequence of increasing reactivity: dimethyl sebacate < adipate < glutarate < succinate. Regardless of the monomer combination, gelation occurred at conversions > 91.5%. The hyperbranched structure was proven by ¹H NMR spectroscopy and the absence of cyclic elements by MALDI‐TOF mass spectrometry. Quantitative acylation of all CH₂OH groups was achieved with an excess of acetic anhydride or methycrylic anhydride. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 231–238, 2009     

Synthesis of ultrahigh molecular weight poly(N‐vinylcarbazole) with a high yield using low‐temperature heterogeneous‐solution polymerization

To prepare ultrahigh molecular weight (UHMW) poly(N‐vinylcarbazole) (PVCZ) with a high conversion, I heterogeneous‐solution‐polymerized N‐vinylcarbazole (VCZ) in methanol/tertiary butyl alcohol (TBA) at 25, 35, and 45 °C with a low‐temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and I investigated the effects of the polymerization conditions on the polymerization behavior and molecular parameters of PVCZ. A low‐polymerization temperature with ADMVN, a heterogeneous system with methanol, and a low chain transfer with TBA proved to be successful in obtaining PVCZ of UHMW [weight‐average molecular weight (M_w) > 3,000,000] and high conversion (>80%) with a smaller temperature rise during polymerization but still of free‐radical polymerization by an azoinitiator. The polymerization rate of VCZ in methanol/TBA at 25 °C was proportional to the 0.97 power of the ADMVN concentration, indicating a heterogeneous nature for the polymerization. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol/TBA at 25 °C with an ADMVN concentration of 0.0001 mol/mol of VCZ, an M_w of 3,230,000 was obtained, with a polydispersity index of 2.4. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 539–545, 2001     

Evolution of the termination rate coefficient in styrene polymerization

Styrene bulk polymerization was conducted at 70 °C with a high initiator concentration, and this ensured that the dominant chain‐stopping mechanism was the combination of free radicals. The evolution of the molecular weight distribution (MWD) of the polymer was measured via the periodic removal of samples during the course of the reaction and their analysis with gel permeation chromatography. The overall termination rate coefficient was independent of the conversion in the dilute regime, as observed from cumulative MWDs. In the middle of the conversion range, the observed trend was compatible with a translational‐diffusion‐controlled mechanism for the termination step. A bimodal distribution of the molecular weights was also found at high conversions and could be explained in terms of an increase in the free‐radical concentration and a very low termination rate coefficient. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 178–187, 2005     

The ligand effect in Ti‐mediated living radical styrene polymerizations initiated by epoxide radical ring opening. 2. Scorpionate and half‐sandwich LTiCl3 complexes

The ligand effect and the reaction conditions for the living radical polymerization of styrene initiated by epoxide radical ring opening was investigated in a series of piano‐stool, Ti(IV) scorpionate and, half‐sandwich metallocenes (LTiCl₃; L = Tp, Cp*, Ind and Cp, where Tp = hydrotris(pyrazol‐1‐ylborato), Cp* = pentamethylcyclopentadienyl, Ind = indenyl and Cp = cyclopentadienyl). The polymerization is mediated by the reversible termination of the growing chains with Ti(III) species derived from Zn reduction of parent Ti(IV) derivatives. A poor performance was observed for TpTiCl₃ because of probable over‐reduction. The strong electron donating effect of Cp* accounts for a strong C? Ti chain end bond and consequently, a living‐like process is observed only at T > 110 °C. However, both Ind and Cp ligands provide a linear dependence of M_n on conversion and narrow polydispersity over a wide range of experimental conditions. Investigation of the effect of temperature and reagent ratios generates an optimum for epoxide/CpTiCl₃/Zn = 1/2/4 at 70–90 °C. On the basis of a combination of steric and electronic properties, the ligands rank as Cp ≥ Ind ? Cp* ? Tp. This trend is different from coordination polymerization, and in conjunction with our previous results on Cp₂TiCl₂, further supports a radical mechanism. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6039–6047, 2005     

Synthesis and structural analysis of functionalized poly (ϵ‐caprolactone)‐based three‐arm star polymers

Hydroxyl‐functionalized three‐arm poly(?‐caprolactone)s (PGCL‐OHs) were synthesized by the ring‐opening polymerization of ?‐caprolactone in the presence of glycerol (as the core) and stannous octoate. The effect of the feed ratio of ?‐caprolactone to glycerol on the ring‐opening polymerization was studied. These three‐arm PGCL‐OHs were then converted into double‐bond‐functionalized three‐arm poly(?‐caprolactone)s (PGCL‐Mas) by the reaction of PGCL‐OH with maleic anhydride in the melt at 130 °C. The quantitative conversion of hydroxyl functionality was achieved at a low molecular weight. The resulting PGCL‐OH and PGCL‐Ma were characterized with gel permeation chromatography, Fourier transform infrared, ¹H NMR, ¹³C NMR, and differential scanning calorimetry. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1127–1141, 2002     

Kinetics of the seeded semicontinuous emulsion copolymerization of methyl methacrylate and butyl acrylate

The effect of a chain‐transfer agent (CTA) on the kinetics and molecular weight distribution of the methyl methacrylate/butyl acrylate semicontinuous emulsion polymerization was investigated. The dodecanethiol had a slight effect on the reaction rate but significantly affected the secondary nucleation. The effect of the CTA concentration on the gel formation and the effect of the reaction conditions on the mass‐transfer limitations of the CTA are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 367–375, 2000     

Alkoxyamine‐mediated “living” radical polymerization: MS investigation of the early stages of styrene polymerization initiated by cumyl‐TEISO

A new series of 1,1,3,3‐tetraethylisoindoline‐2‐oxyl (TEISO)‐based alkoxyamines was prepared. The half‐lives for thermal dissociation indicated that the most sterically congested cumyl‐TEISO alkoxymine had the greatest potential as an initiator for the polymerization of monomers at lower temperatures. The polymerization of styrene at 110 °C gave a linear evolution of M_n with conversion in the early stages. Further evidence for the “living” nature was given by the polydispersities of the polymers that remained low (M_w/M_n = 1.13–1.27) throughout the polymerization (up to 80% conversion). No polymer was formed for the styrene system in a reasonable time below 100 °C. High‐performance liquid chromatographic/mass spectrometric investigations of the distribution of trapped oligomers containing one to nine monomer units formed at 60 °C revealed that the trapping of oligomeric cumyl–styryl radicals by TEISO is irreversible at this temperature. Methyl methacrylate polymerized with cumyl‐TEISO at 60–70 °C, although the initial high rates of polymerization soon decreased to zero at low conversions (10–15%), and the high polydispersities (M_w/M_n = 1.42–1.73) indicated significant side reactions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1232–1241, 2001