N‐Bromosuccinimide as a thermal iniferter for radical polymerization

N‐Bromosuccinimide (NBS) was used as a thermal iniferter for the initiation of the bulk polymerizations of methyl methacrylate, methyl acrylate, and styrene. The polymerizations showed the characteristics of a living polymerization: both the yields and the molecular weights of the resultant polymers increased linearly as the reaction time increased. The molecular weight distributions of the polymers were 1.42–1.95 under the studied conditions. The resultant polymers could be used as macroiniferters to reinitiate the polymerization of the second monomer. The copolymers poly(methyl methacrylate)‐b‐polystyrene and polystyrene‐b‐poly(methyl methacrylate) were obtained and characterized. End‐group analysis of the resultant poly(methyl methacrylate), poly(methyl acrylate), and polystyrene confirmed that NBS behaved as a thermal iniferter. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2567–2573, 2005     

Atom transfer radical polymerization of styrene and methyl methacrylate catalyzed by FeCl2/iminodiacetic acid

The atom transfer radical polymerization of styrene and methyl methacrylate with FeCl₂/iminodiacetic acid as the catalyst system in bulk was successfully implemented at 70 and 110 °C, respectively. The polymerization was controlled: the molecular weight of the resultant polymer was close to the calculated value, and the molecular weight distribution was relatively narrow (weight‐average molecular weight/number‐average molecular weight ∼ 1.5). Block copolymers of polystyrene‐b‐poly(methyl methacrylate) and poly(methyl methacrylate)‐b‐poly(methyl acrylate) were successfully synthesized, confirming the living nature of the polymerization. A small amount of water added to the reaction system increased the reaction rate and did not affect the living nature of the polymerization system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4308–4314, 2000     

Covalent stabilization of nanostructures: Robust block copolymer templates from novel thermoreactive systems

Structurally robust block copolymer templates with feature sizes of approximately 10 nm were prepared from functionalized poly(methyl methacrylate)‐b‐polystyrene block copolymers. By the inclusion of benzocyclobutene crosslinking groups in the polystyrene block, the covalent stabilization of thin films to both thermal treatment and solvent exposure became possible. In addition, the crosslinking of the poly(styrene‐benzocyclobutene) domains at 220 °C, followed by the removal of poly(methyl methacrylate), provided a robust, crosslinked nanostructure with greater processing and fabrication potential. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1028–1037, 2005     

SET‐LRP of methyl methacrylate initiated with CCl4 in the presence and absence of air

Single electron transfer‐living radical polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The synthesis of poly(methyl methacrylate) via SET‐LRP in dimethyl sulfoxide (DMSO) by using CCl₄ as initiator is demonstrated in this work. Resorting to a rather simple Cu(0)/Me₆‐TREN catalyst a method was established that allowed for the straightforward design of well‐defined poly(methyl methacrylate). The reactions were performed at various temperatures (25, 50, 60, and 80 °C) and complete monomer conversion could be achieved. The polymerizations obeyed first order kinetic, the molecular weights increased linearly with conversion and the polymers exhibited narrow molecular weight distributions all indicating the livingness of the process. By providing a small amount of hydrazine to the reaction mixture the polymerization could be conducted in presence of air omitting the need for any elaborated deoxygenation procedures. This methodology offers an elegant way to synthesize functionalized poly(methyl methacrylate) with perfect control over the polymerization process as well as molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2243–2250, 2010     

Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition–fragmentation chain transfer polymerization

The reversible addition–fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert‐butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2‐cyanoprop‐2‐yl dithiobenzoate as chain‐transfer agents was studied in toluene solutions at 70 °C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number‐average molecular weight versus the conversion revealed controlled polymerization features with chain‐transfer constants expected between 1.0 and 10. A series of poly(tert‐butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 × 10⁴ to 3.0 × 10⁴, as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert‐butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple‐detector size exclusion chromatograph. The Mark–Houwink–Sakurada parameters for poly(tert‐butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and ¹H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5680–5689, 2005     

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     

Synthesis and characterization of multifunctional polymers via atom transfer radical polymerization of N‐(ω′‐alkylcarbazolyl) methacrylates initiated by Ru(II) polypyridyl chromophores

A series of poly(N‐(ω′‐alkylcarbazoly) methacrylates) tris(bipyridine) Ru‐centered bifunctional polymers with good filming, thermal, and solubility properties were synthesized and characterized. Atom transfer radical polymerization (ATRP) of N‐(ω′‐alkylcarbazoly) methacrylates in solution was used, where Ru complexes with one and three initiating sites acted as metalloinitiators with NiBr₂(PPh₃)₂ as a catalyst. ATRP reaction conditions with respect to polymer molecular weights and polydispersity indices (PDI) of the target bifunctional polymers were examined. Electronic absorption and emission spectra of the resultant functional polymers provided evidence of chromophore presence within a single polymeric chain. The thermal properties of all polymers were also investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and these analyses have indicated that these polymers possess higher thermal stabilities than poly(methyl methacrylate) (PMMA) obtained via free radical polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6057–6072, 2005     

Synthesis of methyl methacrylate,styrene, and isobutylene multiblock copolymers using atom transfer and cationic polymerization

ABCBA‐type pentablock copolymers of methyl methacrylate, styrene, and isobutylene (IB) were prepared by the cationic polymerization of IB in the presence of the α,ω‐dichloro‐PS‐b‐PMMA‐b‐PS triblock copolymer [where PS is polystyrene and PMMA is poly(methyl methacrylate)] as a macroinitiator in conjunction with diethylaluminum chloride (Et₂AlCl) as a coinitiator. The macroinitiator was prepared by a two‐step copper‐based atom transfer radical polymerization (ATRP). The reaction temperature, ?78 or ?25 °C, significantly affected the IB content in the resulting copolymers; a higher content was obtained at ?78 °C. The formation of the PIB‐b‐PS‐b‐PMMA‐b‐PS‐b‐PIB copolymers (where PIB is polyisobutylene), prepared at ?25 (20.3 mol % IB) or ?78 °C (61.3 mol % IB; rubbery material), with relatively narrow molecular weight distributions provided direct evidence of the presence of labile chlorine atoms at both ends of the macroinitiator capable of initiation of cationic polymerization of IB. One glass‐transition temperature (T_g), 104.5 °C, was observed for the aforementioned triblock copolymer, and the pentablock copolymer containing 61.3 mol % IB showed two well‐defined T_g's: ?73.0 °C for PIB and 95.6 °C for the PS–PMMA blocks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3823–3830, 2005     

Catalytic effect of dimethyl sulfoxide in the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical polymerization of methyl methacrylate at 0–90 °C initiated with CH3CHClI as a model compound for α,ω‐di(iodo)poly(vinyl chloride) chain ends

A variety of conditions, including catalysts [CuCl, CuI, Cu₂O, and Cu(0)], ligands [2,2′‐bipyridine (bpy), tris(2‐dimethylaminoethyl)amine (Me₆‐TREN), polyethyleneimine, and hexamethyl triethylenetetramine], initiators [CH₃CHClI, CH₂I₂, CHI₃, and F(CF₂)₈I], solvents [diphenyl ether, toluene, tetrahydrofuran, dimethyl sulfoxide (DMSO), dimethylformamide, ethylene carbonate, dimethylacetamide, and cyclohexanone], and temperatures [90, 25, and 0 °C] were studied to assess previous methods for poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) synthesis by the living radical block copolymerization of methyl methacrylate (MMA) initiated with α,ω‐di(iodo)poly(vinyl chloride). CH₃CHClI was used as a model for α,ω‐di(iodo)poly(vinyl chloride) employed as a macroinitiator in the living radical block copolymerization of MMA. Two groups of methods evolved. The first involved CuCl/bpy or Me₆‐TREN at 90 °C, whereas the second involved Cu(0)/Me₆‐TREN in DMSO at 25 or 0 °C. Related ligands were used in both methods. The highest initiator efficiency and rate of polymerization were obtained with Cu(0)/Me₆‐TREN in DMSO at 25 °C. This demonstrated that the ultrafast block copolymerization reported previously is the most efficient with respect to the rate of polymerization and precision of the PMMA‐b‐PVC‐b‐PMMA architecture. Moreover, Cu(0)/Me₆‐TREN‐catalyzed polymerization exhibits an external first order of reaction in DMSO, and so this solvent has a catalytic effect in this living radical polymerization (LRP). This polymerization can be performed between 90 and 0 °C and provides access to controlled poly(methyl methacrylate) tacticity by LRP and block copolymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1935–1947, 2005     

Reverse atom transfer radical polymerization of vinyl monomers with Fe[SC(S)NEt2]3 alone as the catalyst

The living radical polymerization of methyl methacrylate and styrene was successfully carried out with diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS)/ferric tri(diethyldithiocarbamate) as a novel reverse atom transfer radical polymerization initiation system in which DCDPS was a hexa‐substituted ethane‐type thermal iniferter, DC was a diethyldithiocarbamate group, and no additional ligands such as nitrogen‐ or phosphine‐based compounds were required. The bulk polymerization of methyl methacrylate was carried out at 95 °C, and that of styrene was carried out at 120 °C. Poly(methyl methacrylate) and polystyrene (PSt) with high molecular weights and quite narrow molecular weight distributions (as low as 1.09 for PSt) were obtained. ¹H NMR spectroscopy revealed the presence of an α‐(carbethoxycyanophenyl)methyl group from the initiator and an ω‐DC group from the catalyst in the obtained polymers. Various chain‐extension reactions under UV light or thermal treatments were successfully conducted to prove the presence and efficient reinitiating of the ω‐DC group. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3464–3473, 2001     

Automated parallel anionic polymerizations: Enhancing the possibilities of a widely used technique in polymer synthesis

Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec‐butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene‐b‐isoprene) and poly(styrene‐b‐methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005     

Catalytic effect of ionic liquids in the Cu2O/2,2′‐bipyridine catalyzed living radical polymerization of methyl methacrylate initiated with arenesulfonyl chlorides

The effect of 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid on the living radical polymerization of methyl methacrylate initiated with arenesulfonyl chlorides and catalyzed by the self‐regulated Cu₂O/2,2′‐bipyridine catalyst was investigated. A dramatic acceleration of the living radical polymerization of methyl methacrylate in this ionic liquid was discovered. This accelerated living radical polymerization maintained an initiation efficiency of 100%, eliminated the induction period of this catalyst, and produced poly(methyl methacrylate) with molecular weight distribution of 1.1 and perfect bifunctional chain‐ends. The kinetic analysis of the living radical polymerization in the presence of ionic liquid demonstrated a rate constant of propagation that follows an almost first order of reaction on the ionic liquid concentration and therefore, the ionic liquid exhibits catalytic effect. The catalytic effect of the ionic liquid facilitated the reduction of the catalyst concentration from stoichiometric to catalytic and allowed the decrease of the polymerization temperature from 80 to 22 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5609–5619, 2005     

Raft polymerization of MMA in the presence of ferrocene: A new way to realize the rate enhancement

Ferrocene (Fe(Cp)₂) was added to a thermal initiation of reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent at 115 °C. It was found that the polymerization was greatly promoted after the addition of Fe(Cp)₂ while retaining the characteristics of a typical RAFT polymerization. It was proposed that the formation of a redox initiation system, in which the poly(methyl methacrylate) peroxide (PMMAP) generated in situ as the oxidizer and Fe(Cp)₂ as the reducer, was possibly the reason for the interesting polymerization phenomenon. Such a redox initiation mechanism was further validated with ascorbic acid (VC) as the reducer instead of Fe(Cp)₂. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3607–3615, 2009     

Synthesis of phosphate end‐functional polymers and application to thermally latent polymeric initiators

Novel phosphates, O‐p‐(hydroxymethyl)benzyl O,O‐diethyl phosphate ( 1 ) and O‐(2‐bromoisobutyryloxymethyl)benzyl O,O‐diethyl phosphate ( 2 ) were synthesized by the reaction of diethyl phosphorochloridate with 1,4‐benzenedimethanol and the successive reaction with 2‐bromoisobutyryl bromide in the presence of triethylamine and submitted to the polymerization of ?‐caprolactone and methyl methacrylate as the initiators. They afforded phosphate end‐functional poly(?‐caprolactone) and poly(methyl methacrylate) with controlled molecular weights and polydispersity ratios by living ring‐opening polymerization and samarium‐induced polymerization. The polymerization of glycidyl phenyl ether (GPE) was carried out with the phosphate end‐functional polymers as the latent polymeric initiators in the presence of ZnCl₂. The polymerization of GPE did not proceed below 90 °C, but it rapidly proceeded to afford poly(GPE) above the temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3832–3840, 2001     

Luminescent polymeric ruthenium complexes with polystyrene‐b‐poly(methyl methacrylate) macroligands: The sequential activation of initiator sites for blocks generated by parallel polymerization mechanisms

The synthesis of polystyrene‐b‐poly(methyl methacrylate) diblock copolymers with a luminescent ruthenium(II) tris(bipyridine) [Ru(bpy)₃] complex at the block junction is described. The macroligand precursor, polystyrene bipyridine‐poly(methyl methacrylate) [bpy(PS–H)(PMMA)], was synthesized via the atom transfer radical polymerization of styrene and methyl methacrylate from two independent, sequentially activated initiating sites. Both polymerization steps resulted in the growth of blocks with sizes consistent with monomer loading and narrow molecular weight distributions (i.e., polydispersity index < 1.3). Subsequent reactions with ruthenium(II) bis(bipyridine) dichloride [Ru(bpy)₂Cl₂] in the presence of Ag⁺ generated the ruthenium tris(bipyridine)‐centered diblock, which is of interest for the imaging of block copolymer microstructures and for incorporation into new photonic materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4250–4255, 2002     

Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization

Well‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at ?78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et₃OBF₄ gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005     

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

The reversible addition–fragmentation chain transfer (RAFT) polymerizations of 2‐naphthyl acrylate (2NA) initiated by 2,2′‐azobisisobutyronitrile were investigated with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as a RAFT agent at various temperatures in a benzene solution. The results of the polymerizations showed that 2NA 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. The polydispersities of the polymer were relatively low up to high conversions in all cases. The chain‐extension reactions of poly(2‐naphthyl acrylate) (P2NA) with methyl methacrylate and styrene successfully yielded poly(2‐naphthyl acrylate)‐b‐poly(methyl methacrylate) and poly(2‐naphthyl acrylate)‐b‐polystyrene block polymers, respectively, with narrow polydispersities. The P2NA obtained by RAFT polymerization had a strong ultraviolet absorption at 270 nm, and the molecular weights had no apparent effect on the ultraviolet absorption intensities; however, the fluorescence intensity of P2NA increased as the molecular weight increased and was higher than that of 2NA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2632–2642, 2005     

A novel fluorine‐containing graft copolymer bearing perfluorocyclobutyl aryl ether‐based backbone and poly(methyl methacrylate) side chains

A series of novel graft copolymers consisting of perfluorocyclobutyl aryl ether‐based backbone and poly(methyl methacrylate) side chains were synthesized by the combination of thermal [2π + 2π] step‐growth cycloaddition polymerization of aryl bistrifluorovinyl ether monomer and atom transfer radical polymerization (ATRP) of methyl methacrylate. A new aryl bistrifluorovinyl ether monomer, 2‐methyl‐1,4‐bistrifluorovinyloxybenzene, was first synthesized in two steps from commercially available reagents, and this monomer was homopolymerized in diphenyl ether to provide the corresponding perfluorocyclobutyl aryl ether‐based homopolymer with methoxyl end groups. The fluoropolymer was then converted to ATRP macroinitiator by the monobromination of the pendant methyls with N‐bromosuccinimide and benzoyl peroxide. The grafting‐from strategy was finally used to obtain the novel poly(2‐methyl‐1,4‐bistrifluorovinyloxybenzene)‐g‐poly(methyl methacrylate) graft copolymers with relatively narrow molecular weight distributions (M_w/M_n ≤ 1.46) via ATRP of methyl methacrylate at 50 °C in anisole initiated by the Br‐containing macroinitiator using CuBr/dHbpy as catalytic system. These fluorine‐containing graft copolymers can dissolve in most organic solvents. This is the first example of the graft copolymer possessing perfluorocyclobutyl aryl ether‐based backbone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Preparation of CO2‐switchable latexes using N‐[3‐(dimethylamino)propyl]‐methacrylamide (DMAPMAm)

CO₂‐switchable polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl methacrylate) (PBMA) latexes were prepared via surfactant‐free emulsion polymerization (SFEP) under a CO₂ atmosphere, employing N‐[3‐(dimethylamino)propyl]methacrylamide (DMAPMAm) as a CO₂‐switchable, water‐soluble, and hydrolytically stable comonomer. The conversion of the SFEP of styrene reaches >95% in less than 5 h. The resulting latexes have near monodisperse particles (PDI ≤ 0.05), as confirmed by DLS and TEM. The latexes could be destabilized by bubbling nitrogen (N₂) and heating at 65 °C for 30 min, and easily redispersed by only bubbling CO₂ for a short time without using sonication. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1059–1066     

Miktoarm star copolymers of poly(ϵ‐caprolactone) from a novel heterofunctional initiator

A novel heterofunctional initiator, synthesized from pentaerythritol in a three step reaction sequence with two ring opening polymerization (ROP) and two atom transfer radical polymerization (ATRP) initiating sites, was used to prepare A₂B₂ miktoarm star copolymers of poly(ε‐caprolactone), PεCL, with polystyrene, PS, poly(methyl methacrylate), PMMA, poly(dimethylaminoethyl methacrylate), PDMAEMA, and poly(2‐hydroxyethyl methacrylate), PHEMA. A₂B miktoarm stars, A being PεCL or poly(δ‐valerolactone), PδVL and B PS were also prepared from ω,ω‐dihydroxy‐PS, synthesized from ω‐Br‐PS and serinol, by ROP of εCL or δVL. All polymers were characterized by size exclusion chromatography, ¹H NMR spectroscopy, and membrane osmometry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5164–5181, 2007