Synthesis of conductive microspheres by radiation polymerization

A conductive monodisperse microspheres consisting of poly(ethylene glycol)dimethacrylate and methyloxycarbonyl-bicyclo[2.2.1]hepta-2,5-diene was synthesized by radiation induced polymerization. Ionic conductivity and relative dielectric constant were found to be greatly dependent on the content of poly(ethylene glycol)methacrylate in the copolymer. The diameter of the microspheres was 0.48-0.86 μm, in which the irradiation was carried out without stabilizer at a dose rate of 20 kGy/h with ⁶⁰Co γ-ray.     

High molecular arborescent polyoxyethylene with hydroxyl containing shell

Arborescent polyoxyethylene of high molar mass (2×10⁵ g/mol) and narrow molar mass distribution was synthesized in a three-stage process. In the first stage a triblock copolymer of ethylene oxide (central block, DP ca. 90) and 2,3-epoxypropanol-1 (short flanking blocks, DP ca. 5) was synthesized. The potassium alcoholate derived from this copolymer was used to initiate the polymerization of ethylene oxide and the subsequent addition of protected glycidol (1-etoxyethyl glycidyl ether). After deprotection the short polyglycidol blocks were used as branching units for the next generation. Repeated step by step process leads to the ‘pom-pom like’ branched polyoxyethylene macromolecules enriched with the reactive hydroxyl groups in the outer shell. The branched structure of the obtained polymers was evidenced by the size exclusion chromatography and NMR spectroscopy.     

Time-resolved gel permeation chromatographic study on poly(N-isopropylacrylamide)-block-poly(ethylene glycol) prepared by soap-free emulsion polymerization

To synthesize an amphiphilic block copolymer of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) (NE), an aqueous soap-free emulsion polymerization system was employed where poly(N-isopropylacrylamide) (PNIPA), polymerized from the radically activated chain ends of poly(ethylene glycol) (PEG), forms micelle cores stabilized by PEG brush chains emanating there from. When this polymerization was carried out at temperatures equal to or higher than 34 °C, narrowly-dispersed NE, which cannot be obtained by solution polymerization, was successfully obtained. To elucidate the living nature of the soap-free emulsion polymerization, time-dependent monomer conversion and molecular weight of NE was investigated by time-resolved gel permeation chromatography (GPC). The results indicate that the compartmentalization of end radicals into micelles cores leads to the quasi-living behavior of the polymerization.     

Synthesis and polymerization of maleimide-type new macromonomer with polystyrene having controlled chain length

A new reactive and functionalized polystyrene with a maleimide moiety at the one polymer end was synthesized with N-(4-(1-chloroethyl)pheyl)maleimide (CEPMI)/SnCl₄/tetra-butylammonium chloride (TBAC) initiating system. The polymer obtained with the CEPMI/SnCl₄/TBAC initiating system under the condition of [TBAC]/[SnCl₄] = 1 was to be maleimide-type macromonomer with polystyrene having controlled molecular weight of polystyrene (VI). VI could be polymerized with anionic and radical initiators to give new type graft polymer (poly[N-(4-ethylphenyl)maleimide]-graft-polystyrene) with controlled chain length with respect to side chains.     

Synthesis of poly(ethylene terephthalate-co-isophthalate) via ring-opening polymerization of their cyclic oligomers

Syntheses of poly(ethylene terephthalate-co-isophthalate) (PET-co-PEI) were achieved via ring-opening copolymerization of corresponding cyclic oligoesters. The ring-opening polymerization (ROP)-PET-co-PEI were prepared by equilibrating an equimolar amount of cyclic oligo(ethylene terephthalate) and cyclic oligo(ethylene isophthalate) using di-n-butyltin oxide catalyst under high concentration conditions at 270 and 290 °C for 8 and 12 h. The copolyesters were obtained in yields of up to 91% with the inherent viscosity (η _inh) of up to 2.89 dl/g indicating the drastically high molecular weight compared with the conventional and ROP routes for the synthesis of PEI. The differential scanning calorimetry data of ROP-PET-co-PEI showed the melting temperatures above 400 °C indicated the potential used in high temperature application.     

Synthesis and Characterization of GAP-PEG Copolymers

ABSTRACT

A series of glycidylazide–poly(ethylene glycol) (GAP-PEG) copolymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) in the presence of poly(ethylene glycol) (PEG) using borontrifluoride etherate (BF₃-etherate) as catalyst, followed by the conversion of the CH₂Cl groups of poly(epichlorohydrin) (PECH) to CH₂N₃ groups. The formation of PECH-b-PEG-b-PECH triblock copolymers was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. The corresponding GAP-b-PEG-b-GAP triblock copolymers were characterized by UV, IR, ¹H NMR, and ¹³C NMR spectroscopy. The copolymers have shown an increment in their molecular weights as the higher analogue molecular weight PEGs were used in the polymerizations. The thermogravimetry-differential thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC) studies of the GAP triblock copolymers indicate an increase in the decomposition temperature of the azide groups of GAP block in the copolymers caused by the introduction of higher molecular weight PEG blocks. GAP-PEG copolymers have shown lower glass transition temperatures than the homo glycidylazide polymer. The nitrogen content of the GAP-PEG copolymers was estimated by various methods and the value was in good agreement with the estimated values.     

Synthesis, isothermal crystallization and micellization of mPEG-PCL diblock copolymers catalyzed by yttrium complex

Amphiphilic biodegradable mPEG-PCL diblock copolymers have been synthesized using rare earth catalyst: yttrium tris(2,6-di-tert-butyl-4-methylphenolate) [Y(DBMP)₃] in the presence of monomethoxy poly(ethylene glycol) (mPEG, M_n = 5000) as macro-initiator. The diblock architecture of the copolymers was thoroughly characterized by ¹H NMR, ¹³C NMR and SEC. The molecular weights of mPEG-PCLs can be well controlled by adjusting the feeding molar ratio of ?-CL to mPEG. Thermal and crystallization behaviors of the diblock copolymers were investigated by DSC and POM (polarized optical microscope). The crystallization property of mPEG-PCL block copolymers depends on the length of PCL blocks. As the molecular weight of PCL block increased, the crystallization ability of mPEG block was visibly restrained. Aqueous micelles were prepared by dialysis method. The critical micelle concentration of the copolymers, which was determined to be 0.9-6.9 mg/L by fluorescence technique, increased with the decreasing of PCL block length. The particle sizes determined by DLS were 30-80 nm increasing with the PCL block length. TEM images showed that these micelles were regularly spherical in shape.     

Synthesis of hydroxyl-capped comb-like poly(ethylene glycol) to develop shell cross-linkable micelles

A novel hydroxyl-capped comb-like poly[poly(ethylene glycol) methacrylate] (PPEGMA) was prepared via atom transfer radical polymerization (ATRP) of α-methylacryloyl-ω-hydroxyl-poly(ethylene glycol) at ambient temperature. The polymerization kinetics of the block copolymer was studied by gel permeation chromatography (GPC) and ¹H NMR. It is of interest to find the well-defined comb-like PEG can associate into micelles, which have hydrophilic PEG shell end-capped by hydroxyl groups. The hydroxyl in the shell were further cross-linked by divinyl sulfone (DVS), which could couple with two capped-end hydroxyl groups. The XPS, TEM, AFM and laser scattering particle size distribution analyzer results revealed that reactive micelles could be cross-linked by DVS. The reactive, cross-linkable micelles with PEG shell may have great potential as new drug carrier and nanoreactor, etc.     

Nanoscale structure of SAN-PEO-SAN triblock copolymers synthesized by atom transfer radical polymerization

Low molecular weight triblock copolymers (TBCs) with poly(styrene-co-acrylonitrile) (SAN) end-blocks and poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) or polycaprolactone (PCL) mid-blocks were synthesized using atom transfer radical polymerization (ATRP). The influence of molecular weight, composition (mid-block mole fraction), and interaction parameter on the crystallinity and on the formation of an ordered nanoscale phase-separated structure was investigated using thermal analysis, X-ray scattering, and electron microscopy. The TBCs with PEO mole fractions of over 0.5 exhibited PEO crystallinities of around 40% (compared to 72% for the PEO homopolymer) and lamellar nanoscale periodicities of around 176 Å (compared to 143 Å for the PEO homopolymer). The TBCs with PEO, PCL or PPO mole fractions of less than 0.5 exhibited relatively low crystallinities and did not exhibit ordered structures. These results emphasize the importance of the mid-block mole fraction in determining the ability to form an ordered nanoscale structure through mid-block crystallization. The ordered structure disappeared on heating the TBCs above the mid-block melting point, but below the SAN glass transition temperature. The crystallinity was reduced significantly in TBCs that were annealed or cast from a solvent.     

Synthesis of poly(1,4-naphthylene) bearing crown ether side chain by asymmetric oxidative coupling polymerization

The oxidative coupling polymerization of racemic-, (R)-, and (S)-2,2′,3,3′-tetrahydroxy-1,1′-binaphthyl derivatives bearing a crown ether moiety was carried out in the presence of a Cu(I) or Cu(II) catalyst with various ligands, such as N,N,N′,N′-tetramethylethylenediamine, (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine, (−)-sparteine [(−)Sp], and (S)-(−)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline). Methanol-insoluble poly(binaphthyl crown ether) with a molecular weight up to M_n=4.1×10³ was synthesized in moderate yields. Polymerization using (−)Sp proceeded in an S-selective manner; the polymer with the highest negative specific rotation was obtained with the (S)-monomer. The obtained polymers exhibited characteristic abilities for chiral recognition toward amino acids, such as 2-phenylglycine hydrochloride and 2-phenylglycine methyl ester hydrochloride.     

Hydrophilic polymer supports grafted by poly(ethylene glycol) derivatives via atom transfer radical polymerization

In this study, a newly structured hydrophilic polymer supports are prepared by the chemical modification (grafting) of the polystyrene-based preformed beads via atom transfer radical polymerization (ATRP) employing the CuBr/PMDETA catalyst system. Hydrophilic monomers including N,N-dimethylacrylamide (DMA) and poly(ethylene glycol) (PEG) macromonomers were grafted onto Merrifield type resin. Based on optical microscopic data, the particle sizes of the resins were increased in the order of 10 μm after the polymerization. This increment indicated that monomers are grafted not only to the particle surface but also to within a polymer matrix. These resins demonstrate well-swellability in polar solvent, and they enable high functional loadings up to 0.7-1.8 mmol g⁻¹. The high loading capacity in polar solvents and favorable mechanical properties of resins render them to have great potential applications in peptide and oligonucletide syntheses.     

Synthesis of rapid responsive gels comprising hydrophilic backbone and poly(N-isopropylacrylamide) graft chains by RAFT polymerization and end-linking processes

A thermosensitive poly(N-isopropylacrylamide) (PNIPAM) grafted gel, which comprises hydrophilic backbone and freely mobile PNIPAM graft chains, was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and end-linking processes. Functional PNIPAM bearing dithiobenzoate end group (-C(S)S-R) was prepared first, and then it was reacted with divinyl compounds to obtain gel. In order to adjust the composition of the gels, two divinyl compounds, N,N-methylenebisacrylamide (BIS) and poly(ethylene glycol) diacrylate (PEGDAC), were used. The cross-linking polymerization mechanism was proposed. The swelling and deswelling kinetics of the hydrogels were measured. The gels exhibit rapid deswelling kinetics. At the same time, they show rapid swelling kinetics within 30 min, whereas a conventional PNIPAM-co-PEG-co-BIS gel with the same feed composition requires more than 10 h to reach swelling equilibrium.     

Synthesis and Characterization of Biocompatible Poly(ethylene glycol)-b-Poly(L-lactide) and Study on Their Electrospun Scaffolds

A series of multiblock copolymer, Poly(L-lactide)-b-Poly(ethylene glycol) (PLLA-b-PEG) were synthesized and characterized by Fourier transform infrared spectra, differential scanning calorimetry and wide angle X-ray diffraction. PLLA-b-PEG fibrous scaffolds were prepared by electrospinning. The morphology of the fibers was affected by the solution concentration and different weight ratio of PLLA/PEG. In comparison with the electrospun PLLA membrane, the electrospun fibrous membranes of PLLA-b-PEG demonstrated an enhanced water absorption percentage and reductive water contact angle. The electrospun PLLA-b-PEG with weight ratio 90/10 and 75/25 fibrous membranes exhibited good flexibility and deformability to be beneficial for tissue engineering scaffolds.     

Synthesis of poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene triblock copolymers by two-step atom transfer radical polymerization

The synthesis of ABC triblock copolymer poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene (PEO-b-PMMA-b-PS) via atom transfer radical polymerization (ATRP) is reported. First, a PEO-Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide, which was subsequently used in the preparation of halo-terminated poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) diblock copolymers under ATRP conditions. Then PEO-b-PMMA-b-PS triblock copolymer was synthesized by ATRP of styrene using PEO-b-PMMA as a macroinitiator. The structures and molecular characteristics of the PEO-b-PMMA-b-PS triblock copolymers were studied by FT-IR, GPC and ¹H NMR.     

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen‐containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s‐b‐polyacrylonitrile, poly(ethylene glycol)s‐b‐poly(acrylonitrile‐co‐vinyl acetate), poly(ethylene glycol)s‐b‐polyacrylamide, poly(ethylene glycol)s‐b‐poly(acrylamide‐co‐vinyl acetate), poly(1‐chloromethyl ethylene glycol)‐bpoly(acrylonitrile‐co‐vinyl acetate), and bis[poly(ethylene glycol terephthalate)]‐b‐poly(acrylonitrile‐co‐vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999     

Miniemulsion polymerization of styrene in the presence of macromonomeric initiators

Macromonomeric azo initiators (macroinimers, MIM) which have the properties of macromonomers, macrocrosslinkers and macroinitiators in a macrostructure were used in miniemulsion polymerization of styrene in the presence or absence of any other stabilizer and initiator. MIMs were prepared from the reaction of 4,4′-dicyano-4,4′-azovaleryl chloride, with poly(ethylene glycol) (PEG) of different molecular weights (400 and 2000 g/mol) and with 4-vinylbenzyl chloride. The stabilizing and initiator efficiency of MIMs and the effect of the chain length of PEG units were evaluated.     

Synthesis, characterization and ring-opening polymerization of a novel six-membered cyclic carbonate bearing pendent allyl ether group

A novel six-membered cyclic carbonate with pendent allyl ether group, 5-allyloxy-1,3-dioxan-2-one (ATMC), was synthesized from glycerol, and the corresponding polycarbonate, poly(5-allyloxy-1,3-dioxan-2-one) (PATMC) was further synthesized by ring-opening polymerization in bulk at 120 °C. Two kinds of catalyst, tin(II) 2-ethylhexanoate (Sn(Oct)₂) and immobilized porcine pancreas lipase on silica particles (IPPL), were employed to perform the polymerization. The structures of the novel monomer and the resulting functional polymers were confirmed by FTIR, ¹H NMR, ¹³C NMR, GPC and DSC. The molecular weight (M_n) of PATMC decreased rapidly with the increase of IPPL or Sn(Oct)₂ concentration. The highest molecular weight (M_n = 48,700 g/mol) of PATMC with the polydispersity of 1.31 was obtained at 0.1 wt% concentration of IPPL for 48 h. Postpolymerization oxidation reactions to epoxidize the unsaturated bonds of the PATMC were also achieved. The epoxide-containing polymers could afford facilities for further modification.     

棒状结构纳米Pd/PEG600复合材料的制备与表征

在超声辐射作用下,以PEG600为还原剂和稳定剂,合成了纳米钯/PEG复合材料.XRD和UV-Vis结果证明了氯化钯被完全还原成钯,TEM显示PEG呈长约0.5μm,直径为50～80nm的棒状结构,并将部分纳米钯粒子包覆在其中.     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry