ESR study on chemical crosslinking reaction mechanisms of polyethylene using a chemical agent—II. The effect of phenolic antioxidants

The effect of antioxidant on the reaction mechanism of chemical crosslinking of polyethylene (PE) with dicumyl peroxide (DCP) at high temperatures was investigated by electron spin resonance (ESR). The antioxidant reacts with the alkyl radicals in PE formed by the thermal decomposition of DCP above 120°C, and disturbs the crosslinking. A phenolic type antioxidant produced the phenoxy radical by the reaction with alkyl radicals formed in PE. It is suggested that the selection of a suitable antioxidant for PE crosslinking can be made by ESR analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2431–2439, 1997     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

Electron spin resonance study on chemical crosslinking reaction mechanisms of polyethylene using a chemical agent. V. Comparison with polypropylene and ethylene‐propylene copolymer

We studied the chemical reaction process of polypropylene (PP), ethylene‐propylene copolymer (EPM), and ethylene‐propylene‐diene copolymer (EPDM) crosslinking induced by dicumyl peroxide (DCP) using electron spin resonance (ESR). Free radicals appeared at an elevated temperature of around 120 °C and the behavior and kinetics of the reaction process were observed at 180 °C. The radical species detected in PP were alkyl type radicals, formed by the abstraction of hydrogen atoms from the tertiary carbon of polymer chains. For EPDM containing a diene component, the radicals were trapped at double bonds in this diene component to form allyl radicals. The resolutions of these spectra were extremely clear; hence, isotropic spectra of these polymer radicals were obtained. We measured the ESR at high temperatures and confirmed that the process of crosslinking induced by DCP was a free radical reaction. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3383–3389, 2000     

Thiol‐terminated polyisobutylene: Synthesis,characterization, and derivatization

Thiol‐terminated polyisobutylene (α,ω‐PIB‐SH) was synthesized from thiourea and α,ω‐bromine‐terminated PIB in a three‐step, one‐pot procedure, using a cosolvent system of 1:1 (v:v) heptane:dimethylformamide. The initial alkylisothiouronium salt was produced at 90 °C. Aqueous base hydrolysis at 110 °C resulted in thiolate chain ends, which were re‐acidified to form telechelic PIB‐SH. ¹H and ¹³C NMR confirmed thiol functionality and complete terminal halogen conversion. Thiol‐based “click” reactions were used to demonstrate PIB‐SH utility. Alkyne‐terminated PIB was synthesized by a phosphine‐catalyzed thiol‐ene Michael addition with propargyl acrylate. Reaction of this product with 6‐mercaptohexanol produced tetrahydroxy‐functional PIB by a sequential thiol‐ene/thiol‐yne procedure. ¹H NMR confirmed the structures of both products. PIB‐SH was reacted with isocyanates in the presence of base to produce polythiourethanes. A model reaction used phenyl isocyanate in THF with catalytic triethylamine. Similar conditions were used to produce PIB‐based thiourethanes with and without a small‐molecule chain extender. Increased molecular weights and thiol group conversion were observed with GPC and ¹H NMR, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Aging of a donor conjugated polymer: Photochemical studies of the degradation of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene]

This article is devoted to the study of the photoaging and thermal aging of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene] (MDMO–PPV; also called OC1C10–PPV) used in organic solar cells. Thin MDMO–PPV films (thickness < 1 μm) were exposed to ultraviolet‐light irradiation (λ > 300 nm) in the presence of air or thermooxidized at 60 °C. The modifications of the chemical structure of the matrix were analyzed with ultraviolet–visible and infrared spectroscopy. The oxidation products that formed were identified by postirradiation treatments, including chemical derivatization reactions. On the basis of the identification of the various products formed, a two‐step radical mechanism is proposed to account for the modification of the chemical structure of the polymeric matrix. It involves first the oxidation of the ether substituent followed by the oxidation of the double bonds. These reactions are responsible for a loss of conjugation of MDMO–PPV, chain scissions, and a decrease in the visible absorbance, which are anticipated to drastically impair the photovoltaic properties of the material. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 317–331, 2007     

Radiation-induced solid-state polymerization of derivatives of methacrylic acid. III. An electron spin resonance study of radical reactions in irradiated octadecyl methacrylate

The electron spin resonance spectrum of gamma-irradiated octadecyl methacrylate (m.p. ≈ 12°C.) was due to a mixture of three radicals formed by (1) loss of a hydrogen atom from the paraffin chain, (2) addition of a hydrogen atom to the double bond, and (3) addition of a monomer molecule to radicals formed by (1) or (2). On warming monomer added to radicals (1) and (2) between ?170 and ?50°C., and above ?50°C. the spectrum was solely due to propagating methacrylate radicals. The total radical concentration decreased slightly at ?150°C. and was then constant up to ?30°C. A marked decrease in radical concentration occurred from ?30 to +12°C., it took place rapidly and reached an equilibrium value after each successive increase in temperature. Differential thermal analysis indicated a solid—solid phase change at ?30°C. When the sample was kept at 0°C. there was no further decrease in radical concentration even with 50% conversion to polymer. With 2% added chloranil the (chloranil)^? was observed to be of about the same concentration as methacrylate radicals. The initial total radical concentration was lower and decreased to zero by 0°C. on warming. No polymer was obtained.     

Polyolefin soluble polyisobutylene oligomer‐bound metallophthalocyanine and azo dye additives

Metallophthalocyanines prepared with polyisobutyl (PIB) substituents have very high solubility in organic solvents including saturated hydrocarbons, toluene, and other low polarity organic solvents. In heptane, PIB‐bound metallophthalocyanines have solubility of about 0.1 g/mL at 25 °C, solubility values that are significantly higher than other substituted metallophthalocyanines. PIB terminally functionalized with metallophthalocyanines as well as PIB containing terminal azo dye groups also dissolve in molten hydrocarbon polymers like polyethylene or polypropylene. Thus, these highly chromogenic PIB‐bound dyes can be incorporated uniformly into the polyolefins to form colored polymer solids on cooling. Because only a low concentration of a highly hydrocarbon compatible dye is used, the crystallinity and thermal properties of the colored polyolefin products are not significantly affected. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 545–551     

One‐pot synthesis of isocyanate and methacrylate multifunctionalized polyisobutylene and polyisobutylene‐based amphiphilic networks

Amphiphilic polymer networks consisting of hydrophilic poly(2‐hydroxyethyl methacrylate) (PHEMA) and hydrophobic polyisobutylene (PIB) chains were synthesized from a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) prepared at ?50 °C in dichloromethane in conjunction with SnCl₄. The isocyanate groups of this random copolymer, PIB(NCO)_n, were subsequently transformed in situ to methacrylate (MA) groups in the dibutyltin dilaurate‐catalyzed reaction with 2‐hydroxyethyl methacrylate (HEMA) at 30 °C. The resulting PIB(MA)_n with number–average molecular weight 8200 and average functionality F_n ～ 4 per chain was in situ copolymerized radically with HEMA at 70 °C, giving rise to the amphiphilic networks containing 41 and 67 mol % HEMA. PHEMA–PIB network containing 43 mol % HEMA was also prepared by radical copolymerization of PIB(MA)_n precursor with HEMA using sequential synthesis. An amphiphilic nature of the resulting networks was proved by swelling in both water and n‐heptane. PIB(NCO)_n and PIB(MA)_n were characterized by FTIR spectroscopy, SEC and the latter also by ¹H NMR spectroscopy. Solid state ¹³C NMR spectroscopy was used for characterization of the resulting PHEMA–PIB networks. Whereas single glass‐transition temperature, T_g = ?67.4 °C, was observed for the rubbery crosslinked PIB prepared by reaction of PIB(NCO)_n with water, the PHEMA–PIB networks containing 67 and 41 mol % HEMA showed two T_g's: ?70.4 and 102.7 °C, and ?63 and 107.2 °C, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2891–2900, 2006     

Living carbocationic polymerization of p-halostyrenes. III. Syntheses and characterization of novel thermoplastic elastomers of isobutylene and p-chlorostyrene

Novel linear and three-arm star radial thermoplastic elastomers (TPE) comprising rubbery polyisobutylene (PIB) center blocks connected to glassy poly(p-chlorostyrene) (PpClSt) outer blocks have been synthesized by sequential monomer addition. For triblock polymer synthesis isobutylene (IB) was added continuously to a bifunctional initiating system (dicumylmethyl ether/TiCl₄) dissolved in CH₃Cl/methylcyclohexane solvent mixture at –80°C. After the living PIB sequence has reached the desired molecular weight p-chlorostyrene (pClSt) was added to produce the PpClSt end blocks. The synthesis conditions for the TPEs were developed with the help of model experiments using the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ initiating system and subsequent PIB-PpClSt diblock syntheses. The triblock and radiol block polymers after solvent extraction exhibited excellent TPE characteristics. Copolymer compositions were determined by ¹H-NMR and UV spectroscopy and further characterization was carried out by GPC, DSC, DMTA, and selective solvent extraction techniques. The TPEs exhibit two T_g's characteristic of glassy PpClSt (129°C) and rubbery PIB (?70°C) segments. Cast TPE films were clear and gave tensile strengths of 1.2-21 MPa with elongations of 460–1500%. Transmission electron microscopy (TEM) of a triblock polymer containing ca. 38 wt % PpClSt suggests cylindrical PpClSt domains of 40–70 nm length and 25–35 nm diam embedded in a PIB matrix.     

The reaction of furfuryl alcohol resins with hexamethylenetetramine: A 13C and 15N high-resolution solid-state NMR study

The reactions between furfuryl alcohol (FA)/poly(furfuryl alcohol) (PFA) and hexamethylenetetramine (HMTA) have been studied by ¹³C and ¹⁵N high-resolution solid-state NMR techniques. Highly crosslinked polymer networks similar to those obtained from the thermal curing of FA resins under acidic condition are formed. Possible reaction pathways are postulated on the basis of changes of chemical structures during the curing; α-substituted furfurylamines are shown to be the initial intermediates. Their further reactions with FA/PFA, together with thermal decomposition, produce methylene linkages between furan rings, resulting in chain extension and crosslinking, which occurs at both the methylene linkages and the 3- or 4-C of furan rings. Various side-products such as amines, imines, amides, imides, and nitriles are also formed during the reactions, and some of these can remain in the resins up to 205°C. The crosslinked network can be heterogeneous with different structures on nanometer scales when higher oligomers of FA resins react with HMTA. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2233–2243, 1997     

Synthesis and properties of novel sulfonated polyimides containing 1,5‐naphthylene moieties

A series of novel sulfonated polyimides (equivalent weight per sulfonic acid = 310–744 g/equiv) containing 10–70 mol % 1,5‐naphthylene moieties were synthesized as potential electrolyte materials for high‐temperature polymer electrolyte fuel cells. The polycondensation of 1,4,5,8‐naphthalene tetracarboxylic dianhydride, 4,4′‐diamino‐2,2′‐biphenyldisulfonic acid, and 1,5‐diaminonaphthalene gave the title polymer electrolytes. The polyimide electrolytes were high‐molecular‐weight (number‐average molecular weight = 36.0–350.7 × 10³ and weight‐average molecular weight = 70.4–598.5 × 10³) and formed flexible and tough films. The thermal properties (decomposition temperature > 260 °C, no glass‐transition temperature), stability to oxidation, and water absorption were analyzed and compared with those of perfluorosulfonic acid polymers. The polyimide containing 20 mol % 1,5‐naphthylene moieties showed higher proton conductivity (0.3 S cm^?1) at 120 °C and 100% relative humidity than perfluorosulfonic acid polymers. The temperature and humidity dependence of the proton conductivity was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3901–3907, 2003     

Oxidation and epoxidation of poly(1,3‐cyclohexadiene)

Poly(1,3‐cyclohexadiene) (PCHD) derivatives were synthesized via facile chemical modification reactions of the residual double bond in the repeat unit. The oxidation and degradation of PCHD was investigated to enable subsequent controlled epoxidation reactions. PCHD exhibited a 15% weight loss at 110 °C in the presence of oxygen. The oxidative degradation, demonstrated by gel permeation chromatography (GPC) and ¹H NMR spectroscopy, was attributed to main‐chain scission. Aldehyde and ether functional groups were introduced into the polymer during the oxidation process. PCHD was quantitatively epoxidized in the absence of deleterious oxidation with meta‐chloroperoxybenzoic acid. ¹H and ¹³C NMR spectroscopy confirmed that polymers with controlled degrees of epoxidation were reproducibly obtained. Epoxidized PCHD exhibited a glass‐transition temperature at 154 °C, which was slightly higher than that of a PCHD precursor of a nearly equivalent molecular weight. Moreover, GPC indicated the absence of undesirable crosslinking or degradation, and the molecular weight distributions remained narrow. The thermooxidative stability of the fully epoxidized polymer was compared to that of the PCHD precursor, and the epoxidized PCHD exhibited an initial weight loss at 250 °C in oxygen, which was 140 °C higher than the temperature for PCHD. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 84–93, 2003     

Importance of active-site reactivity and reaction conditions in the preparation of hyperbranched polymers by self-condensing vinyl polymerization: Highly branched vs. linear poly[4-(chloromethyl)styrene] by metal-catalyzed “living” radical polymerization

The self-condensing vinyl polymerization of 4-(chloromethyl)styrene using metal-catalyzed living radical polymerization catalyzed by the complex CuCl/2,2′-bipyridyl has been attempted. Given the unequal reactivity of the two potential propagating species in this system, a variety of polymerization conditions were tested to optimize the extent of branching in the products. Typical reaction conditions included polymerization in the bulk, or preferably in chlorobenzene solution, with catalyst to monomer ratios in the range 0.01–0.30, temperatures of 100–130°C, and reaction times from 0.1 to 32 h. Polymers with weight average molecular weights between 3 × 10³ and 1.6 × 10⁵ and different extents of branching are formed as evidenced by size-exclusion chromatography, light scattering, and NMR analysis of the reaction products. The influence of reaction conditions on the molecular weight and branching of the resulting polymers is discussed in detail. In sharp contrast to an earlier report, the weight of evidence suggests that, at a catalyst to monomer ratio of 0.01, an almost linear polymer is obtained, while a high catalyst to monomer ratio favors the formation of a branched structure. As a result of the unequal reactivity of the primary and secondary benzylic halide reactive sites, growth occurs by a modified self-condensing vinyl polymerization mechanism that involves incorporation of the largely linear vinyl-terminated fragments formed early on in the polymerization into the vinyl polymer, to afford an irregularly branched structure. Chemical transformations involving the numerous benzylic halide functionalities of the highly branched polymer have been investigated. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 955–970, 1998     

Precision synthesis and characterization of thymine‐functionalized polyisobutylene

A new two‐step synthesis of polyisobutylene (PIB) with precisely one thymine functionality per chain (PIB‐T) is reported. The primary hydroxyl‐functionalized PIB (PIB‐OH) precursor was prepared by direct functionalization via living carbocationic polymerization of isobutylene initiated by the α‐methylstyrene epoxide/TiCl₄ system. Matrix assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐ToF MS) of a low molecular weight PIB‐OH precursor demonstrated the effectiveness of direct functionalization by this method. A PIB‐acrylate precursor (PIB‐Ac) was obtained from such a PIB‐OH, and the PIB‐T was subsequently prepared by Michael addition of thymine across the acrylate double bond. MALDI‐ToF MS of the products verified that all polymer chains carried precisely one thymine group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3501–3506, 2010     

Highly fluorinated low‐molecular‐weight photoresists for optical waveguides

A series of highly fluorinated polymers were synthesized by copolymerization of 2,3,4,5,6‐pentafluorostyrene (PFS) and fluorinated styrene derivate monomer (FSDM). Their chemical structure were confirmed by ¹H NMR, ¹³C NMR, and ¹⁹F NMR spectra. The refractive index and cross‐linking density of the polymers can be tuned and controlled by monitoring the feed ratio of comonomers. A series of negative‐type low‐molecular‐weight fluorinated photoresists (NFPs) were prepared by composing of fluorinated polystyrene derivates (FPSDs), diphenyl iodonium salt as a photoacid generator (PAG) and solvent. The polymer films prepared from NFP by photocuring exhibited excellent chemical resistance and thermal stabilities (T_d ranged from 230.5 to 258.1 °C). A clear negative pattern was obtained through direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.25 dB/cm at 1550 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Mechanism of thermal degradation of urea-formaldehyde polycondensates

The thermal degradation to 500°C of urea-formaldehyde polycondensate occurs in four successive steps. In each step, partial volatilisation takes place while the polymer undergoes chemical modification to give progressively more stable structures.Below 200°C methylene ether bridges are transformed into methylene bridges and branching and crosslinking reactions occur with maximum rates at 125°C and 165°C, respectively. Above 200°C radicals formed by chain scission induce the formation of cyclic structures in the polymer which undergoes extensive fragmentation above 300°C. Water, formaldehyde, carbon monoxide and dioxide, methane, ammonia, monomethylamine and trimethylamine are the gaseous products evolved.By combining data on the chemical modifications and gases evolved in each step, reaction mechanisms are proposed.     

Radiooxidation of fluoropolymers: Identification of oxidation products

Radiation effects on fluoropolymers induced by high‐energy irradiation were investigated. Poly(fluorovinylidene‐co‐hexafluoropropylene) [P(VDF‐HFP)] films were irradiated with γ rays in air. Peroxy radicals formed by irradiation in the presence of oxygen were partially converted into more stable products such as hydroperoxides, alcohols, and acids. These oxidation products were identified by Fourier transform infrared spectroscopy. Specific chemical treatments were carried out to identify and separate overlapping absorption bands. Model compounds were also used. On the basis of the results, a mechanism of degradation for γ‐irradiated P(VDF‐HFP) is proposed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1509–1517, 2003     

Synthesis and characterization of two novel star blocks: tCum[poly(isobutylene‐b‐norbornadiene)]3 and tCum[poly(norbornadiene‐b‐isobutylene)]3

Two structurally closely related three‐arm star blocks were synthesized and characterized: tCum(PIB‐b‐PNBD)₃ and tCum(PNBD‐b‐PIB)₃ [where tCum (tricumyl) stands for the phenyl‐1,3,5‐tris(‐2‐propyl) fragment and PIB and PNBD are polyisobutylene and polynorbornadiene, respectively]. The syntheses were accomplished in two stages: (1) the preparation of the first (or inner) block fitted with appropriate chlorine termini capable of initiating the polymerization of the second (or outer) block with TiCl₄ and (2) the mediation of the polymerization of the second block. Therefore, the synthesis of tCum(PIB‐b‐PNBD)₃ was effected with tCum(PIB‐Cl^t)₃ [where Cl^t is tert‐chlorine and number‐average molecular weight (M_n) = 102,000 g/mol] by the use of TiCl₄ and 30/70 CH₃Cl/CHCl₃ solvent mixtures at ?35 °C. PNBD homopolymer contamination formed by chain transfer was removed by selective precipitation. According to gel permeation chromatography, the M_n's of the star blocks were 107,300–109,200 g/mol. NMR spectroscopy (750 MHz) was used to determine structures and molecular weights. Differential scanning calorimetry (DSC) indicated two glass‐transition temperatures (T_g's), one each for the PIB (?65 °C) and PNBD (232 °C) phases. Thermogravimetric analysis thermograms showed 5% weight losses at 293 °C in air and at 352 °C in N₂. The synthesis of tCum(PNBD‐b‐PIB)₃ was achieved by the initiation of isobutylene polymerization with tCum(PNBD‐Cl^sec)₃ (where Cl^sec is sec‐chlorine and M_n = 2900 g/mol) by the use of TiCl₄ in CH₃Cl at ?60 °C. DSC for this star block (M_n = 14,200 g/mol) also showed two T_g's, that is, at ?67 and 228 °C for the PIB and PNBD segments, respectively. It is of interest that the Cl^sec terminus of PNBD, , readily initiated isobutylene polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 740–751, 2003     

Nanostructured ion-conductive films: Layered assembly of a side-chain liquid-crystalline polymer with an imidazolium ionic moiety

An ion-conductive mesogenic monomer with an imidazolium ionic moiety has been designed to obtain self-assembled materials forming ionic layers. Self-standing polymer films are prepared by in situ photopolymerization of the monomer that forms homeotropic monodomain on a normal glass substrate in the smectic A phase. Macroscopically oriented, layered nanostructures are formed in the film. The ionic conductivity parallel to the smectic layer has been measured for the oriented film. In the smectic A phase at 150 °C, the magnitude of conductivity is about 10⁻² S cm⁻¹. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3486–3492, 2003     

Electrochromic material containing unsymmetrical substituted N,N,N′,N′‐tetraaryl‐1,4‐phenylenediamine: Synthesis and their optical,electrochemical, and electrochromic properties

A novel dibromo compound containing unsymmetrical substituted bi‐triarylamine was synthesized. A conjugated polymer was prepared via the Suzuki coupling from the newly prepared dibromo compound and 9,9‐dioctylfluorene‐2,7‐bis(trimethyleneboronate). The glass transition temperature (T_g) of the conjugated polymer was 140 °C, 10% weight‐loss temperatures (T_d10) in nitrogen was 458 °C, and char yield at 800 °C in nitrogen higher than 64%. Cyclic voltammogram of the polymer film cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited two reversible oxidation redox couples at 0.70 and 1.10 V versus Ag/Ag⁺ in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from yellow green of the neutral form to the dark green and blue of oxidized forms at applied potentials ranging from 0 to 1.3 V. The color switching time and bleaching time were 4.25 and 7.22 s for 860 nm and 5.51 s and 6.48 s for 560 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1469–1476, 2010