Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry study on copolymers obtained by the alternating copolymerization of bis(γ‐lactone) and epoxide with potassium tert‐butoxide

Oligomer samples obtained by the anionic copolymerization of a bis(γ‐lactone), 2,8‐dioxa‐1‐methylbicyclo[3.3.0]octane‐3,7‐dione ( 1 ), and glycidyl phenyl ether with potassium tert‐butoxide have been analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. The MALDI‐TOF mass spectra of these cooligomers show well‐resolved signals that can be reliably assigned to linear, alternating cooligomers that have carboxylate chain ends or alkoxide chain ends and cyclic ones. The formation of these three series of cooligomers suggests that the polymerization process involves concomitant intermolecular transesterification and intramolecular back‐biting. The intramolecular back‐biting reaction causes the formation of cyclic cooligomers, whereas the intermolecular transesterification causes the reduction of the molecular weight and the transformation of the alkoxide active chain end into a carboxylate chain end. The MALDI‐TOF mass spectrometry study has shown that an excess of monomer 1 enhances the selectivity of propagation by increasing the probability of the attack of the alkoxide chain end to 1 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2643–2649, 2005     

Chain‐transfer reaction in the radical polymerization of di‐n‐butyl itaconate at high temperatures

Radical polymerizations of di‐n‐butyl itaconate were investigated. Unexpected resonances (C resonances) were observed in ¹³C NMR spectra of C?O of poly(di‐n‐butyl itaconate)s [poly(DBI)s] obtained at temperatures higher than 60 °C, although two kinds of carbonyl groups showed splittings due to triad tacticities in the spectra of polymers obtained at lower temperatures. The poly(DBI)s formed by the different kinds of initiators or formed in the presence of chain‐transfer agents showed hardly any changes in the intensities of the C resonances; this indicated that the C resonances were not due to the structures formed through initiating and terminating reactions. The poly(DBI)s obtained at different yields showed only a slight increase in the intensities of the C resonances with the yield, which suggested that the C resonances were not attributable to the intermolecular chain‐transfer reaction to the monomer and/or polymer. However, the intensities of the C resonances significantly increased with a decreasing feed monomer concentration; this suggested that intramolecular chain‐transfer reactions took place at high temperatures. Furthermore, a Cu complex‐catalyzed atom transfer radical polymerization mechanism was revealed to be effective for suppressing the intramolecular chain‐transfer reaction at 60 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2415–2426, 2002     

Synthesis of a thermoresponsive shell‐crosslinked 3‐layer onion‐like polymer particle with a hyperbranched polyglycerol core

A novel thermoresponsive shell crosslinked three‐layer onion‐like polymer particles were prepared using hyperbranched polyglycerol (PG) as parents compound, the periphery hydroxyl groups of PG were transformed into trithiocarbonates (? SC(S)S? ) first; then, it was used as chain transfer agent to prepare star‐like block copolymer of N‐isopropyl acrylamide (NIPA) and N,N‐dimethylaminoethyl acrylate (DMA) in sequence via reversible addition fragmentation chain transfer (RAFT) process. Thus, a three‐layer polymer, PG? [SC(S)S? (DMA)? b? (NIPA)]_n, was obtained. The middle layer of poly(DMA) was then crosslinked with 1,8‐diiodoctane, and the resulting onion‐like three‐layer polymer showed a lower critical solution temperature (LCST) in water because of the outer layer of poly(NIPA). The LCST value only slightly depended on the crosslinking degree. Finally, the ? SC(S)S? were transformed into thiols by sequential treating with sodium borohydride and formic acid; thus, the core molecule was chemically detached from the crosslinked shell and a novel shell crosslinked polymer particle was obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5652–5660, 2005     

Synthesis of poly(m‐phenylene) and poly(m‐phenylene)‐block‐ poly(3‐hexylthiophene) with low polydispersities

Well‐defined poly(m‐phenylene) (PMP), which is poly(1,3‐dibutoxy‐m‐phenylene), was successfully synthesized via Grignard metathesis polymerization. PMP with a reasonably high number‐average molecular weight (M_n) of 25,900 and a very low polydispersity index of 1.07 was obtained. The polymerization of a Grignard reagent monomer, 1‐bromo‐2,4‐dibutoxy‐5‐chloromagnesiobenzene, proceeded in a chain‐growth manner, probably due to the meta‐substituted design producing a short distance between the MgCl and Br groups and thereby making a smooth nickel species (? C? Ni? C? ) transfer to the intramolecular chain end (? C? Ni? Br) over a benzene ring. PMP showed a good solubility in the common organic solvents, such as tetrahydrofuran, CH₂Cl₂, and CHCl₃. Furthermore, a new block copolymer comprised of PMP and poly(3‐hexylthiophene) was also prepared. The tapping mode atomic force microscopy image of the surface of the block copolymer thin film on a mica substrate showed a nanofibril morphology with a clear contrast. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis of multihydroxyl branched polyethers by cationic copolymerization of 3,3‐bis(hydroxymethyl)oxetane and 3‐ethyl‐3‐(hydroxymethyl)oxetane

The cationic ring‐opening polymerization of 3,3‐bis(hydroxymethyl)oxetane (BHMO) and the copolymerization of BHMO with 3‐ethyl‐3‐(hydroxymethyl)oxetane (EOX) were studied. Medium molecular weight polymers (number‐average molecular weight ≈ 2 × 10³) were obtained in bulk polymerization. Poly[3,3‐bis(hydroxymethyl)oxetane], as highly insoluble, was only characterized by gel permeation chromatography and NMR methods in the esterified form. Copolymers of BHMO and EOX that were slightly soluble in organic solvents were characterized in more detail. In a copolymerization from a 1:1 mixture, the comonomers were consumed at equal rates. Matrix‐assisted laser desorption/ionization time‐of‐flight analysis confirmed that a random 1:1 copolymer was formed. ¹³C NMR analysis indicated that in contrast to previously described homopolymers of EOX in which the degree of branching was limited, the homopolymers of BHMO were highly branched. This pattern was preserved in the copolymers; EOX units were predominantly linear, whereas BHMO units were predominantly branched. The copolymerization of BHMO with EOX provides, therefore, a route to multihydroxyl branched‐polyethers with various degrees of branching containing ? OH groups exclusively as ≡C? CH₂? OH units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1991–2002, 2002     

Cationic Polymerization of 3‐Ethyl‐3‐hydroxymethyloxetane in an Ionic Liquid

Summary: Cationic ring‐opening polymerization of 3‐ethyl‐3‐hydroxymethyloxetane (EOX) in a neutral ionic liquid (1‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmim][BF₄]) leading to a multihydroxyl, branched polyether proceeds readily to nearly quantitative conversion. Because of the relatively high polarity of ionic liquids, intermolecular hydrogen bonding leading to the formation of aggregates is reduced considerably. On the other hand, intramolecular hydrogen bonding facilitating intramolecular chain transfer is not significantly affected and the molecular weights of polymers are in the same range as those obtained in bulk polymerization or polymerization in organic solvents.

     

pH‐responsive destabilization and facile bioconjugation of new hydroxyl‐terminated block copolymer micelles

New hydroxyl‐terminated amphiphilic block copolymers (HO‐ABPs) having pendant t‐butyl groups for pH‐responsiveness and terminal OH groups for bioconjugation are reported. These HO‐ABPs consist of hydrophilic poly(oligo(ethylene oxide) monomethyl ether methacrylate) and hydrophobic poly(t‐butyl methacrylate) blocks and were synthesized by a consecutive atom transfer radical polymerization in the presence of an OH‐terminated bromine initiator. Aqueous self‐assembly of HO‐ABPs resulted in colloidally stable micellar aggregates being capable of encapsulating hydrophobic guest molecules. They were nontoxic to cells and destabilized in response to low pH. A facile bioconjugation of HO‐ABP micelles for active targeting is demonstrated by conjugation with biotin (vitamin H) and competitive assay exhibiting >93% ABP chains conjugated with biotin in each micelle. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of allyl end‐block functionalized poly(ε‐caprolactone)s and their facile post‐functionalization via thiol–ene reaction

A simple and facile strategy for the functionalization of commercial poly(ε‐caprolactone) diols (PCLs) with pendant functionalities at the polymer chain termini is described. Well‐defined allyl‐functionalized PCLs with varying numbers of allyl end‐block side‐groups were synthesized by cationic ring‐opening polymerization of allyl glycidyl ether using PCL diols as macroinitiators. Further functionalization of the allyl‐functionalized PCLs was realized via the UV‐initiated radical addition of a furan‐functionalized thiol to the pendant allyl functional groups, showing the suitability for post‐modification of the PCL materials. Changes in polymer structure as a result of varying the number of pendant functional units at the PCL chain termini were demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 928–939     

Synthesis of α‐maleimide‐ω‐dienyl heterotelechelic poly(methyl methacrylate) and its cyclization by the intramolecular Diels–Alder reaction

The synthesis of heterotelechelic poly(methyl methacrylate) (PMMA) containing α‐maleimide‐ω‐dienyl end‐groups and its subsequent intramolecular cyclization are described. The anionic polymerization of methyl methacrylate was carried out with 3‐tert‐butyldimethylsilyloxypropyl‐1‐lithium and 5‐bromo‐1,3‐pentadiene as the initiator and terminator, respectively, to synthesize α‐hydroxy‐ω‐dienyl‐PMMA. The introduction of the maleimide group to the α chain end by the reaction of the sodium salt of the polymer with N‐(3‐chloromethylphenyl)‐maleimide or N‐(3‐bromomethylphenyl)‐maleimide was not successful because of the nucleophilic addition of alkoxide to the carbon carbon double bond of the maleimide group. When 4,4′‐bismaleimidediphenylether was allowed to react with the alkoxide, the aimed α‐maleimide‐ω‐dienyl‐PMMA was obtained in a good yield. Ring closure by the intramolecular Diels–Alder reaction was carried out by the heating of the dilute polymer solution in tetrahydrofuran. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 237–246, 2000     

Synthesis and characterization of soluble polyimides derived from 2,2′‐Bis(3,4‐dicarboxyphenoxy)‐9,9′‐spirobifluorene dianhydride

The synthesis of aromatic poly(ether imide)s containing spirobifluorene units in the polymer backbone is described. 2,2′‐Bis(3,4‐dicarboxyphenoxy)‐9,9′‐spirobifluorene dianhydride, which was used as a new monomer, was synthesized with 2,2′‐dihydroxy‐9,9′‐spirobifluorene as the starting material. In the spiro‐segment, the rings of the connected bifluorene were orthogonally arranged. This bis(ether anhydride) monomer was employed in reactions with a variety of aromatic diamines to furnish poly(ether imide)s, involving an initial ring‐opening polycondensation and subsequent chemically induced cyclodehydration. Excellent solubility in common organic solvents at room temperature, good optical transparency, and high thermal stability are the prominent characteristic features of these new polymers, which can be attributed to the presence of spiro‐fused orthogonal bifluorene segments along the polymer chain. The glass‐transition temperatures of the polyimides were 240–293 °C, and the 5% weight‐loss temperatures were greater than 500 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 262–268, 2002     

Higher α‐olefin polymerizations catalyzed by rac‐Me2Si(1‐C5H2‐2‐CH3‐4‐tBu)2Zr(NMe2)2/Al(iBu)3/[Ph3C][B(C6F5)4]

Polymerizations of higher α‐olefins, 1‐pentene, 1‐hexene, 1‐octene, and 1‐decene were carried out at 30 °C in toluene by using highly isospecific rac‐Me₂Si(1‐C₅H₂‐2‐CH₃‐4‐^t Bu)₂Zr(NMe₂)₂ (rac‐1) compound in the presence of Al(iBu)₃/[CPh₃][B(C₆F₅)₄] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the π‐ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(α‐olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1‐hexene), and then increased from poly(1‐hexene) to poly(1‐decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1‐pentene) > poly(1‐hexene) > poly(1‐octene) > poly(1‐decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). ¹H NMR analysis showed that vinylidene group resulting from β‐H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1687–1697, 2000     

Synthesis and chemical modification of hyperbranched polyethers with terminal hydroxy groups by the anionic ring‐opening polymerization of 3‐alkyl‐3‐hydroxymethyl oxetanes

The anionic ring‐opening polymerization of oxetanes containing hydroxyl groups was carried out with potassium tert‐butoxide as an initiator in the presence of 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding multifunctional hyperbranched polymers: poly(3‐ethyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 2200–4100 in 83–95% yields, and poly(3‐methyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 4600–5200 in 70–95% yields. The synthesized poly(3‐ethyl‐3‐hydroxymethyloxetane)s and poly(3‐methyl‐3‐hydroxymethyloxetane)s were hyperbranched polyethers containing an oxetane moiety and many hydroxy groups at the ends. The postpolymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane)s was performed in the presence of potassium tert‐butoxide and 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding polymers with higher molecular weights in good yields. The cationic polymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane) derivatives was carried out with boron trifluoride etherate as an initiator and was followed by alkaline hydrolysis; this yielded a new branched polymer, a poly(hyperbranched polyether), with many pendant hydroxy groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3739–3750, 2004     

Development of catalyst‐transfer condensation polymerization. Synthesis of π‐conjugated polymers with controlled molecular weight and low polydispersity

We describe the development of chain‐growth condensation polymerization for the synthesis of well‐defined π‐conjugated polymers via a new polymerization mechanism, catalyst‐transfer polymerization. We first studied the condensation polymerization of Grignard‐type hexylthiophene monomer with a Ni catalyst as a part of our research on chain‐growth condensation polymerization, and found that this polymerization also proceeded in a chain‐growth polymerization manner. However, the polymerization mechanism involving the Ni catalyst was different from that of previous chain‐growth condensation polymerizations based on substituent effects; the Ni catalyst catalyzed the coupling reaction of the monomer with the polymer, followed by the transfer of Ni(0) to the terminal C? Br bond of the elongated molecule. This catalyst‐transfer condensation polymerization is generally applicable for the synthesis of polythiophene with an etheric side chain and poly(p‐pheneylene), as well as for the synthesis of polyfluorene via the Pd‐catalyzed Suzuki–Miyaura coupling reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 753–765, 2008     

Synthesis of hydrophilic/CO2‐philic poly(ethylene oxide)‐b‐poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) block copolymers via controlled/living radical polymerizations and their properties in liquid and supercritical CO2

Hydrophilic/CO₂‐philic poly(ethylene oxide)‐b‐poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) block copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, iodine transfer polymerization (ITP), and atom transfer radical polymerization (ATRP) in the presence of either degenerative transfer agents or a macroinitiator based on poly(ethylene oxide). In this work, both RAFT and ATRP showed higher efficiency than ITP for the preparation of the expected copolymers. More detailed research was carried out on RAFT, and the living character of the polymerization was confirmed by an ultraviolet (UV) analysis of the ? SC(S)Ph or ? SC(S)S? C₁₂H₂₅ end groups in the polymer chains. The quantitative UV analysis of the copolymers indicated a number‐average molecular weight in good agreement with the value determined by ¹H NMR analysis. The properties of the macromolecular surfactants were investigated through the determination of the cloud points in neat liquid and supercritical CO₂ and through the formation of water‐in‐CO₂ emulsions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2405–2415, 2004     

Synthesis of amphiphilic copolymer brushes: Poly(ethylene oxide)‐graft‐polystyrene

A well‐defined amphiphilic copolymer brush with poly(ethylene oxide) as the main chain and polystyrene as the side chain was successfully prepared by a combination of anionic polymerization and atom transfer radical polymerization (ATRP). The glycidol was first protected by ethyl vinyl ether to form 2,3‐epoxypropyl‐1‐ethoxyethyl ether and then copolymerized with ethylene oxide by the initiation of a mixture of diphenylmethylpotassium and triethylene glycol to give the well‐defined polymer poly(ethylene oxide‐co‐2,3‐epoxypropyl‐1‐ethoxyethyl ether); the latter was hydrolyzed under acidic conditions, and then the recovered copolymer of ethylene oxide and glycidol {poly(ethylene oxide‐co‐glycidol) [poly(EO‐co‐Gly)]} with multiple pending hydroxymethyl groups was esterified with 2‐bromoisobutyryl bromide to produce the macro‐ATRP initiator [poly(EO‐co‐Gly)_(ATRP). The latter was used to initiate the polymerization of styrene to form the amphiphilic copolymer brushes. The object products and intermediates were characterized with ¹H NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, Fourier transform infrared, and size exclusion chromatography in detail. In all cases, the molecular weight distribution of the copolymer brushes was rather narrow (weight‐average molecular weight/number‐average molecular weight < 1.2), and the linear dependence of ln[M₀]/[M] (where [M₀] is the initial monomer concentration and [M] is the monomer concentration at a certain time) on time demonstrated that the styrene polymerization was well controlled. This method has universal significance for the preparation of copolymer brushes with hydrophilic poly(ethylene oxide) as the main chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4361–4371, 2006     

Alternating π‐conjugated copolymer of dithiafulvene with 2,2′‐bipyridyl units

A π‐conjugated polymer containing a dithiafulvene unit and a bipyridyl unit was prepared by cycloaddition polymerization of aldothioketene derived from 5,5′‐diethynyl‐2,2′‐bipyridine. Ultraviolet–visible (UV–vis) absorption spectra showed that the π‐conjugation system of the polymer expanded more effectively than that of a benzene analogue of poly(dithiafulvene) obtained from 1,4‐diethynylbenzene. Cyclic voltammetry measurements indicated that the dithiafulvene–bipyridyl polymer was a weaker electron‐donor polymer than the benzene analogue. These results supported the idea that the incorporation of the electron‐accepting bipyridyl moiety into conjugated poly(dithiafulvene) induced an intramolecular charge‐transfer (CT) effect between the units. Treatment of the dithiafulvene–bipyridyl polymer with bis(2,2′‐bipyridyl)dichlororuthenium (II) [Ru(bpy)₂Cl₂] afforded a ruthenium–polymer complex. A cyclic voltammogram of the complex showed broad redox peaks, which indicated electronic interaction between the dithiafulvene and tris(bipyridyl) ruthenium complex. The dithiafulvene–bipyridyl polymer formed CT complexes with 7,7,8,8‐tetracycanoquinodimethane (TCNQ) in dimethyl sulfoxide. The UV–vis absorption indicated that the resulting CT complex contained anion radical of TCNQ and partially charge‐transferred TCNQ. The polymer showed an unusually high electrical conductivity of 3.1 × 10^?4 S/cm in its nondoped state due to the effective donor–acceptor interaction between the bipyridine unit and the dithiafulvene unit. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4083–4090, 2001     

Synthesis and characterization of well‐defined poly(2‐hydroxyethyl methacrylate‐co‐styrene)‐graft‐poly(ε‐caprolactone) by sequential controlled polymerization

A new graft copolymer, poly(2‐hydroxyethyl methacrylate‐co‐styrene) ‐graft‐poly(?‐caprolactone), was prepared by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with coordination‐insertion ring‐opening polymerization (ROP). The copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 60 °C in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDTB) using AIBN as initiator. The molecular weight of poly (2‐hydroxyethyl methacrylate‐co‐styrene) [poly(HEMA‐co‐St)] increased with the monomer conversion, and the molecular weight distribution was in the range of 1.09 ～ 1.39. The ring‐opening polymerization (ROP) of ?‐caprolactone was then initiated by the hydroxyl groups of the poly(HEMA‐co‐St) precursors in the presence of stannous octoate (Sn(Oct)₂). GPC and ¹H‐NMR data demonstrated the polymerization courses are under control, and nearly all hydroxyl groups took part in the initiation. The efficiency of grafting was very high. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5523–5529, 2004     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Bis‐dendritic polyethylene prepared by ring‐opening metathesis polymerization in the presence of bis‐dendritic chain transfer agents

The synthesis of ABA triblock copolymers is described, in which the A blocks are poly(benzyl ether) dendrons and the B block is polycyclooctene or polyethylene. Bis‐dendritic cis‐olefins were synthesized and used as chain transfer agents in ring‐opening metathesis polymerization of cyclooctene in a process that inserts the dendrons at the polymer chain‐ends. Evaluation of the polymer products by spectroscopic, chromatographic, and titration methods supports their triblock structure. Hydrogenation of the unsaturated polycyclooctene B‐block of these ABA triblock copolymers provides the first reported synthesis of bisdendritic polyethylene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5429–5439, 2005     

RAFT‐mediated synthesis of poly[(oligoethylene glycol) methyl ether acrylate] brushes for biological functions

The synthesis of poly[(oligoethylene glycol) methyl ether acrylate] [poly(OEGA)] brushes was achieved via reversible addition‐fragmentation chain transfer (RAFT) polymerization and used to selectively immobilize streptavidin proteins. Initially, gold surfaces were modified with a trithiocarbonate‐based RAFT chain transfer agent (CTA) by using an ester reaction involving a gold substrate modified with 11‐mercapto‐1‐undecanol and bis(2‐butyric acid)trithiocarbonate. poly(OEGA) brushes were then prepared via RAFT‐mediated polymerization from the surface‐immobilized CTA. The immobilization of CTA on the gold surface and the subsequent polymer formation were followed by ellipsometry, X‐ray photoelectron spectroscopy, grazing angle‐Fourier transform infrared spectroscopy, atomic force microscopy, and water contact‐angle measurements. RAFT‐mediated polymerization method gave CTA groups to grafted poly(OEGA) termini, which can be converted to various biofunctional groups. The terminal carboxylic acid groups of poly(OEGA) chains were functionalized with amine‐functionalized biotin units to provide selective attachment points for streptavidin proteins. Fluorescence microscopy measurements confirmed the successful immobilization of streptavidin molecules on the polymer brushes. It is demonstrated that this fabrication method may be successfully applied for specific protein recognition and immobilization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012