Highly efficient and well‐controlled ambient temperature RAFT polymerization of glycidyl methacrylate under visible light radiation

A range of well‐defined poly(glycidyl methacrylate) (PGMA) polymers and their corresponding block copolymers were synthesized via 2‐cyanoprop‐2‐yl(4‐fluoro) dithiobenzoate or CPFDB‐mediated ambient temperature reversible addition fragmentation chain transfer radical polymerization or RAFT polymerization under environmentally friendly visible light radiation (λ = 405–577 nm), using a (2,4,6‐trimethylbenzoyl) diphenylphosphine oxide photoinitiator. As comparison, CPFDB‐mediated ambient temperature RAFT polymerizations of glycidyl methacrylate (GMA) under both full‐wave radiation (λ = 254–577 nm) and long‐wave radiation (λ = 365–577 nm) were also studied in this article. The results indicated that CPFDB moieties were significantly photolyzed under either full‐wave radiation or long‐wave radiation, thus undermining the controlled behavior of these RAFT processes. Whereas this photolysis was significantly suppressed under visible light radiation, thus CPFDB functionalities exerted well control over RAFT process, leading to a remarkably living behavior up to 90% GMA monomer conversions. This strategy facilitates the facile synthesis of well‐defined PGMA polymers. More importantly, under visible light radiation, a relatively high initial molar ratio of GMA to CPFDB and TPO led to shortening initialization period of RAFT process and accelerating overall polymerization rate. These effects are remarkably in favor of the facile synthesis of well‐defined PGMA polymers and PGMA‐based copolymers with high molecular weights. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5091–5102, 2007     

Living free‐radical polymerization of styrene under a constant source of γ radiation

Living polymerization of styrene was observed using γ radiation as a source of initiation and 1‐phenylethyl phenyldithioacetate as a reversible addition–fragmentation chain transfer (RAFT) agent. The γ radiation had little or no detrimental effect on the RAFT agent, with the molecular weight of the polymer increasing linearly with conversion (up to the maximum measured conversions of 30%). The polymerization had kinetics (polym.) consistent with those of a living polymerization (first order in monomer) and proportional to the square root of the radiation‐dose rate. This initiation technique may facilitate the grafting of narrow polydispersity, well‐defined polymers onto existing polymer surfaces as well as allow a wealth of kinetic experiments using the constant radical flux generated by γ radiation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 19–25, 2002     

Are o‐nitrobenzyl (meth)acrylate monomers polymerizable by controlled‐radical polymerization?

We report on the controlled‐radical polymerization of the photocleavable o‐nitrobenzyl methacrylate (NBMA) and o‐nitrobenzyl acrylate (NBA) monomers. Atom transfer radical polymerization (ATRP), reversible addition‐fragmentation chain transfer polymerization (RAFT), and nitroxide‐mediated polymerization (NMP) have been evaluated. For all methods used, the acrylate‐type monomer does not polymerize, or polymerizes very slowly in a noncontrolled manner. The methacrylate‐type monomer can be polymerized by RAFT with some degree of control (PDI ∼ 1.5) but leading to molar masses up to 11,000 g/mol only. ATRP proved to be the best method since a controlled‐polymerization was achieved when conversions are limited to 30%. In this case, polymers with molar masses up to 17,000 g/mol and polydispersity index as low as 1.13 have been obtained. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6504–6513, 2009     

α‐Cyanobenzyl dithioester reversible addition–fragmentation chain‐transfer agents for controlled radical polymerizations

A series of new reversible addition–fragmentation chain transfer (RAFT) agents with cyanobenzyl R groups were synthesized. In comparison with other dithioester RAFT agents, these new RAFT agents were odorless or low‐odor, and this made them much easier to handle. The kinetics of methyl methacrylate radical polymerizations mediated by these RAFT agents were investigated. The polymerizations proceeded in a controlled way, the first‐order kinetics evolved in a linear fashion with time, the molecular weights increased linearly with the conversions, and the polydispersities were very narrow (～1.1). A poly[(methyl methacrylate)‐block‐polystyrene] block copolymer was prepared (number‐average molecular weight = 42,600, polydispersity index = 1.21) from a poly(methyl methacrylate) macro‐RAFT agent. These new RAFT agents also showed excellent control over the radical polymerization of styrenics and acrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1535–1543, 2005     

Reversible addition‐fragmentation chain transfer polymerization of a typical hydrophobic monomer of styrene within microreactor of shell‐corona hollow microspheres suspending in water

Reversible addition‐fragmentation chain transfer (RAFT) polymerization of a typical hydrophobic monomer of styrene within microreactor of shell‐corona hollow microspheres of poly(styrene‐co‐methacrylic acid) suspending in water is studied. The shell‐corona hollow microspheres contain a hydrophilic corona of poly(methacrylic acid) (PMAA) and a cross‐linked polystyrene shell, which can suspend in water because of the hydrophilic corona of PMAA. The size of the shell‐corona hollow microspheres is about 289 nm and the extent of the microcavity of the hollow microsphere is 154 nm. These shell‐corona hollow microspheres can act as microreactor, within which the typical hydrophobic monomer of styrene, the RAFT agent of S‐benzyl dithiobenzoate and the initiator of 2,2′‐azobisisobutyronitrile can be encapsulated and RAFT polymerization of styrene takes place in well controlled manner in water. It is found that the resultant polymer of polystyrene has a competitively low polydispersity index and its number‐average molecular weight linearly increases with monomer conversion. The method is believed to be a new strategy of RAFT polymerization of hydrophobic monomer in aqueous solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

2‐Cyanoprop‐2‐yl dithiobenzoate mediated reversible addition–fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. ¹H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007     

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

Theoretical simulations showed that for controlled/living radical polymerization in an emulsion system, some of the earliest born particles could be superswollen to a size close to 1 μm. We hypothesized that the superswelling of these particles would lead to colloidal instability. Under the guidance of the simulation results, reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of methyl methacrylate (MMA) was carried out. Experimental results showed that increasing the initiation rate, surfactant level, and targeted molecular weight could improve the colloidal stability of the RAFT polymerization of MMA in an emulsion. The experimental results were in full accord with the theoretical predictions. The poor control of the molecular weight and polydispersity index was found to have a close relationship with the colloidal instability. For the first time, we demonstrated that RAFT polymerization could successfully be implemented with little coagulum, good control of the molecular weight, and a low polydispersity index with the same process used for traditional emulsion polymerization but with higher surfactant levels and initiation rates. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:2837–2847, 2006     

A strategy for synthesis of ion‐bonded amphiphilic miktoarm star copolymers via supramolecular macro‐RAFT agent

Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization using an ion‐bonded macromolecular RAFT agent (macro‐RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6‐bis(bromomethyl)‐isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion‐bonded supramolecular macro‐RAFT agent was obtained through the interaction between the tertiary amino group and 2‐dodecylsulfanylthiocarbonylsulfanyl‐2‐methyl propionic acid (DMP). Finally, ion‐bonded amphiphilic miktoarm star copolymer, (PSt)₂‐poly(N‐isopropyl‐acrylamide)₂, was prepared by RAFT polymerization of N‐isopropylacrylamide (NIPAM) in the presence of the supramolecular macro‐RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of ¹H‐NMR, FTIR, and GPC techniques. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5805–5815, 2008     

Controlled polymerization of N‐isopropylacrylamide with an activated methacrylic ester

A copolymer of N‐isopropylacrylamide with the N‐hydroxysuccinimide ester of methacrylic acid has found use in a variety of applications. Here we report our efforts to gain control over the molecular weight distribution of this copolymer with controlled radical polymerization methods, such as atom transfer radical polymerization, reversible addition–fragmentation transfer (RAFT), and nitroxide‐mediated polymerization. We have found that RAFT is capable of affording these copolymers with a polydispersity index of 1.1–1.2. Our results for all three polymerizations are reported. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6340–6345, 2004     

Synthesis of statistical and block copolymers containing adamantyl and norbornyl moieties by reversible addition‐fragmentation chain transfer polymerization

The synthesis of statistical and block copolymers, consisting of monomers often used as resist materials in photolithography, using reversible addition‐fragmentation chain transfer (RAFT) polymerization is reported. Methacrylate and acrylate monomers with norbornyl and adamantyl moieties were polymerized using both dithioester and trithiocarbonate RAFT agents. Block copolymers containing such monomers were made with poly(methyl acrylate) and polystyrene macro‐RAFT agents. In addition to have the ability to control molecular weight, polydispersity, and allow block copolymer formation, the polymers made via RAFT polymerization required end‐group removal to avoid complications during the photolithography. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 943–951, 2010     

Dispersion RAFT polymerization of 4‐vinylpyridine in toluene mediated with the macro‐RAFT agent of polystyrene dithiobenzoate: Effect of the macro‐RAFT agent chain length and growth of the block copolymer nano‐objects

The dispersion reversible addition‐fragmentation chain transfer (RAFT) polymerization of 4‐vinylpyridine in toluene in the presence of the polystyrene dithiobenzoate (PS‐CTA) macro‐RAFT agent with different chain length is discussed. The RAFT polymerization undergoes an initial slow homogeneous polymerization and a subsequent fast heterogeneous one. The RAFT polymerization rate is dependent on the PS‐CTA chain length, and short PS‐CTA generally leads to fast RAFT polymerization. The dispersion RAFT polymerization induces the self‐assembly of the in situ synthesized polystyrene‐b‐poly(4‐vinylpyridine) block copolymer into highly concentrated block copolymer nano‐objects. The PS‐CTA chain length exerts great influence on the particle nucleation and the size and morphology of the block copolymer nano‐objects. It is found, short PS‐CTA leads to fast particle nucleation and tends to produce large‐sized vesicles or large‐compound micelles, and long PS‐CTA leads to formation of small‐sized nanospheres. Comparison between the polymerization‐induced self‐assembly and self‐assembly of block copolymer in the block‐selective solvent is made, and the great difference between the two methods is demonstrated. The present study is anticipated to be useful to reveal the chain extension and the particle growth of block copolymer during the RAFT polymerization under dispersion condition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of ultra‐high molecular weight polymers by controlled production of initiating radicals

This study demonstrates that the gradual and slow production of initiating radicals (i.e., hydroxyl radicals here) is the key point for the synthesis of ultra‐high molecular weight (UHMW) polymers via controlled radical polymerization. Hydrogen peroxide (H₂O₂) and ferrous iron (Fe²⁺) react via Fenton redox chemistry to initiate RAFT polymerization. This work presents two enzymatic‐mediated (i.e., Bio‐Fenton‐RAFT and Semi Bio‐Fenton‐RAFT) and one syringe pump‐driven Fenton‐RAFT polymerization processes in which the initiating radicals are carefully and gradually dosed into the reaction solution. The “livingness” of the synthesized UHMW polymers is demonstrated by chain extension and aminolysis experiments. Zimm plots obtained from static light scattering (SLS) technique are used to characterize the UHMW polymers. This Fenton‐RAFT polymerization provides access to polymers of unprecedented UHMW (M_w ~ 20 × 10⁶ g mol^?1) with potential in diverse applications. The UHMW polymers made via the controlled Fenton‐RAFT polymerization by using a syringe pump shows that it is possible to produce such materials through an easy‐to‐set up and scalable process. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1922–1930     

Facile one‐pot/one‐step technique for preparation of side‐chain functionalized polymers: Combination of SET‐RAFT polymerization of azide vinyl monomer and click chemistry

An azido‐containing functional monomer, 11‐azido‐undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side‐chain functionalized polymer could be prepared by one‐pot/one‐step technique, which is combination of SET‐RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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     

Aqueous RAFT polymerization of N‐isopropylacrylamide‐mediated with hydrophilic macro‐RAFT agent: Homogeneous or heterogeneous polymerization?

Aqueous RAFT polymerization of N‐isopropylacrylamide (NIPAM) mediated with hydrophilic macro‐RAFT agent is generally used to prepare poly(N‐isopropylacrylamide) (PNIPAM)‐based block copolymer. Because of the phase transition temperature of the block copolymer in water being dependent on the chain length of the PNIPAM block, the aqueous RAFT polymerization is much more complex than expected. Herein, the aqueous RAFT polymerization of NIPAM in the presence of the hydrophilic macro‐RAFT agent of poly(dimethylacrylamide) trithiocarbonate is studied and compared with the homogeneous solution RAFT polymerization. This aqueous RAFT polymerization leads to the well‐defined poly(dimethylacrylamide)‐b‐poly(N‐isopropylacrylamide)‐b‐poly(dimethylacrylamide) (PDMA‐b‐PNIPAM‐b‐PDMA) triblock copolymer. It is found, when the triblock copolymer contains a short PNIPAM block, the aqueous RAFT polymerization undergoes just like the homogeneous one; whereas when the triblock copolymer contains a long PNIPAM block, both the initial homogeneous polymerization and the subsequent dispersion polymerization are involved and the two‐stage ln([M]_o/[M])‐time plots are indicated. The reason that the PNIPAM chain length greatly affects the aqueous RAFT polymerization is discussed. The present study is anticipated to be helpful to understand the chain extension of thermoresponsive block copolymer during aqueous RAFT polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Emulsion and controlled miniemulsion polymerization of the renewable monomer γ‐methyl‐α‐methylene‐γ‐butyrolactone

The kinetics of free‐radical emulsion polymerization of γ‐methyl‐α‐methylene‐γ‐butyrolactone (MeMBL), a renewable monomer related to methyl methacrylate, are presented in detail for the first time, and stable polymer latices are prepared. The effects of different reaction parameters on free‐radical emulsion polymerization of MeMBL are presented. Homogeneous nucleation is asserted to be the dominant path for particle formation. Miniemulsion copolymerization of MeMBL and styrene is also reported. In this case, the homogeneous nucleation process appears limited when using an oil soluble initiator. Both the RAFT miniemulsion polymerizations and RAFT bulk polymerizations are well controlled and narrow polydispersity copolymers are produced. Rate retardation is observed in the RAFT miniemulsion polymerizations compared with the free‐radical polymerization and RAFT bulk polymerizations and the possible causes of the retardation are discussed. The reactivity ratios of MeMBL and styrene in RAFT bulk copolymerization are also determined. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5929–5944, 2008     

Polymerization of styrene in alcohol/water mediated by a macro‐RAFT agent of poly(N‐isopropylacrylamide) trithiocarbonate: From homogeneous to heterogeneous RAFT polymerization

The reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in alcohol/water mixture mediated with the poly(N‐isopropylacrylamide) trithiocarbonate macro‐RAFT agent (PNIPAM‐TTC) is studied and compared with the general RAFT dispersion polymerization in the presence of a small molecular RAFT agent. Both the homogeneous/quasi‐homogeneous polymerization before particle nucleation and the heterogeneous polymerization after particle nucleation are involved in the PNIPAM‐TTC‐mediated RAFT polymerization, and the two‐stage increase in the molecular weight (M_n) and nanoparticle size of the synthesized block copolymer is found. In the initial homogeneous/quasi‐homogeneous polymerization, the M_n and nanoparticle size slowly increase with monomer conversion, whereas the M_n and particle size quickly increase in the subsequent heterogeneous RAFT polymerization, which is much different from those in the general RAFT dispersion polymerization. Besides, the PNIPAM‐TTC‐mediated RAFT polymerization runs much faster than the general RAFT dispersion polymerization. This study is anticipated to be helpful to understand the polymer chain extension through RAFT polymerization under dispersion conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

RAFT‐mediated batch emulsion polymerization of styrene using poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] trithiocarbonate as both surfactant and macro‐RAFT agent

Poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] trithiocarbonate, which contains the reactive trithiocarbonate group and the appending surface‐active groups, is used as both surfactant and macromolecular reversible addition‐fragmentation chain transfer (macro‐RAFT) agent in batch emulsion polymerization of styrene. Under the conditions at high monomer content of ～20 wt % and with the molecular weight of the macro‐RAFT agent ranging from 4.0 to 15.0 kg/mol, well‐controlled batch emulsion RAFT polymerization initiated by the hydrophilic 2‐2′‐azobis(2‐methylpropionamidine) dihydrochloride is achieved. The polymerization leads to formation of nano‐sized colloids of the poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride]‐b‐ polystyrene‐b‐poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] triblock copolymer. The colloids generally have core‐shell structure, in which the hydrophilic block forms the shell and the hydrophobic block forms the core. The molecular weight of the triblock copolymer linearly increases with increase in the monomer conversion, and the values are well‐consistent with the theoretical ones. The molecular weight polydispersity index of the triblock copolymer is below 1.2 at most cases of polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Reversible addition–fragmentation transfer polymerization of p‐nitrophenyl acrylate and synthesis of diblock copolymers poly(p‐nitrophenyl acrylate)‐b‐polystyrene

Poly(p‐nitrophenyl acrylate)s (PNPAs) with different molecular mass and narrow polydispersity were successfully synthesized for the first time by reversible addition–fragmentation transfer (RAFT) polymerization with azobisisobutyronitrile (AIBN) as an initiator and [1‐(ethoxy carbonyl) prop‐1‐yl dithiobenzoate] as the chain‐transfer agent. Although the molecular mass of PNPAs can be controlled by the molar ratio of NPA to RAFT agent and the conversion, a trace of homo‐PNPA was found, especially at the early stage of polymerization. The dithiobenzoyl‐terminated PNPA obtained was used as a macro chain‐transfer agent in the successive RAFT block copolymerization of styrene (St) with AIBN as the initiator. After purification by two washings with cyclohexane and nitromethane to remove homo‐PSt and homo‐PNPA, the pure diblock copolymers, PNPA‐b‐PSt's, with narrow molecular weight distribution were obtained. The structural analysis of polymerization products by ¹H NMR and GPC verified the formation of diblock copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4862–4872, 2004     

Kinetic modeling of controlled living microemulsion polymerizations that use reversible addition–fragmentation chain transfer

Reversible addition–fragmentation chain transfer (RAFT) polymerization is a useful technique for the formation of polymers with controlled architectures and molecular weights. However, when used in the polymerization of microemulsions, RAFT agents are only able to control the polymer molecular weight only at high RAFT concentrations. Here, a kinetic model describing RAFT microemulsion polymerizations is derived that predicts the reaction rates, molecular weight polydispersities, and particle size. The model predicts that at low RAFT concentrations, the RAFT agent will be consumed early in the reaction and that this will result in uncontrolled polymerization in particles nucleated late in the reaction. The higher molecular weight polydispersity that is observed in RAFT microemulsion polymerizations is the result of this uncontrolled polymerization. The model also predicts a shift in the conversion at which the maximum reaction rate occurs and a decrease in the particle size with increasing RAFT concentration. Both of these trends are also consistent with those observed experimentally. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6055–6070, 2006