Papers by Keyword: Atom Transfer Radical Polymerization (ATRP)

Abstract: Different molecular weight of block coupling agents with well-defined structures have been synthesized successfully by atom transfer radical polymerization (ATRP) from styrene (St), butyl methacrylate (BMA) and 3-methoxyacryloyl-propyltrimethoxyl silicon (KH-570) are as monomer. The structures and compositions of macromolecular coupling agents have been characterized by means of infrared spectrum (FT-IR), ultraviolet spectrum (UV), nuclear magnetic resonance spectroscopy (¹H-NMR) and gel permeation chromatography (GPC). And their effects on the polystyrene/silica (PS/SiO₂) composite materials have been studied. The results show that interface compatibility and mechanical properties of composite materials containing macromolecule coupling agents are improved significantly. The composite materials with block macromolecular coupling agents possess more excellent comprehensive performance. Furthermore, the impact strength increased by 110% when comparing with composite materials which are not modified by the coupling agents.

Abstract: Two approaches of improving the toughness of polypropylene (PP)-based composites reinforced by natural cellulose fibers were developed. The surface modification of cellulose fibrils (CMF) or fiber by either in-situ grafting polymerization of butyl acrylate (BA) on CMF surface via an atom transfer radical polymerization (ATRP) or adsorbing the cationic polymeric latex with core-shell structure on fiber surfaces was performed; and resulting fibers or CMF were used as reinforments in an attempt to enhance the toughness of the PP-based composites. The results of mechanical properties indicated that the flexure, tensile, and impact strengths of the CMF-g-PBA reinforced composites were all improved. The cellulose fibres treated by cationic latex also showed the same trend. The optimal dosage of latex for hydrophobic-modifying fibers was also identified.

Abstract: To improve the dispersibility of silica nanoparticles in dimethacrylate-based dental restorative composite resins, an efficient way was proposed to surface modify silica nanoparticles with polymer grafts. Firstly, silica nanoparticles reacted with 3-aminopropyl-triethoxysilane and 2-bromoisobutyryl bromide to obtain silica with the derived atom transfer radical polymerization (ATRP) initiators, which subsequently initiated the polymerization of methyl methacrylate to fabricate poly(methyl methacrylate) grafted silica nanohybrids. These nanohybrids could be well dispersed into bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) resin and had good interfacial bonding to the resin matrix. With the addition of modified silica nanopaticles, the flexural strength of the photo-cured composite resin was significantly increased in comparison with that of the unmodified group.

Abstract: A novel approach to modify polymeric pigment dispersants with polysiloxanes was developed based on the sequential atom transfer radical polymerization (ATRP) of styrene (St) and tert-butyl acrylate (tBA), using multifunctional α-bromoisobutyryl-containing poly (dimethylsiloxane) (PDMS-Br_m) as the macroinitiators and CuBr/N,N,N,N,N- pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The PDMS-Br_m macroinitiators were obtained from the sequential hydrosilylation of commercially available methyl polysiloxanes containing SiH groups with allyl alcohol and then α-bromoisobutyryl bromide. And then, a series of well-defined comb-like graft copolymers with a PDMS backbone and several polystyrene-block-poly (tert-butyl acrylate) (PS-b-PtBA) side-chains were synthesized via ATRP. After hydrolyzing the tert-butyl groups, the comb-like copolymers may serve as multifunctional dispersing agents in the pigment printing.

Abstract: Novel well-defined ABA-type triblock copolymers, (PMAIPGal-b-PLA-b-PMAIPGal), were synthesized by a three-step procedure: (a) melt polycondensation of L-lactic acid using stannous chloride (SnCl₂•2H₂O) as a catalyst, resulting in a hydroxyl-terminated prepolymer by alkyd condensation with 1,4-butanediol, followed by (b) esterification of the PLA hydroxyl end-groups with 2-bromoisobutyryl bromide, and (c) ATRP of 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPGal) by the bromoisobutyryl initiating groups. The resultant copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The biocompatible and biodegradable copolymers have potential applications as tissue engineering biomaterials or controlled release drug delivery systems.

Abstract: A novel liquid crystalline polymer bearing azobenzene groups in both main chain and side chain has been successfully synthesized by atom transfer radical polymerization (ATRP). Dual bromide-terminated azobenzene was used as the initiator for the ATRP of azobenzene-containing monomer (M6C). The structure of the resulting polymer was confirmed by nuclear magnetic resonance (NMR), and the molecular weight and its dispersity was characterized by gel permeation chromatography (GPC). The mesomorphic properties of this novel polymer were characterized by means of polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The results demonstrated that this polymer can form mesophases.

Abstract: Stimuli-responsive water-soluble and amphiphilic polymers have attracted much attention because their micelles can be produced or destroyed by changing the temperatute, pH, ionic strength, and solvent polarity. In this work, a triply hydrophilic block copolymer of poly (ethylene glycol) and poly (methacrylic acid-co-dimethylamine ethyl methacrylate) [PEO-P(MAA-co-DMAEMA)] was synthesized and characterized. The copolymer system is believed to have the potential for drug delivery applications due to the biocompatibility of MAA and DMAEMA.

Abstract: Poly(N-isopropylacrylamide)(PNIPAM) with terminal aromatic groups were synthesized by atom transfer radical polymerization (ATRP), using N-isopropylacrylamide as monomer and phenyl 2-chloropropionate, (4’-phenyl)phenyl 2-chloropropionate and (2’,6’-diphenyl)phenyl 2-chloropropionate as initators. Then novel functional complexes of poly(N-isopropylacrylamide) and Eu(III) (PNIPAM-Eu(III)) with thermosensitive and fluorescent properties were synthesized and characterized by X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy. Eu(III) was bonded to nitrogen and oxygen atoms in the polymer chain of PNIPAM and formed the complexes of PNIPAM-Eu(III). The lower critical solution temperatures (LCSTs) of PNIPAM-Eu(III) were slightly greater compared with that of PNIPAM. Europium(III) complexes had excellent fluorescence performance, the fluorescence spectrum present characteristic emission of Europium(III) at 613 nm.

Abstract: The ATRP of N-isopropylacrylamide (NIPAM) was carried out in DMF/water at 60 °C to afford a novel linear end-functionalized poly(N-isopropylacrylamide) with acetylated β-CD (AcCD-PNIPAM) and the structures of the products were characterized. The number-average molecular weight (M_n) and the polydispersity index (PDI) of the polymer were obtained from gel permeation chromatography (GPC) analysis. The end-functionalized PNIPAM with β-CD (CD-PNIPAM) was obtained by deacetylation from AcCD-PNIPAM. The lower critical solution temperature (LCST) for the aqueous solutions of CD-PNIPAM, measured by means of ultraviolet-visible spectroscopy (UV-vis), was 4~5 °C higher than that of AcCD-PNIPAM. Ferrocene was included into CD-PNIPAM with mole ratio of 1:1 and the inclusion complex was characterized by cyclic voltammetry (CV) technology.

Abstract: Biocompatible and biodegradable synthetic materials have attracted considerable attention during the past two decades. In this work, a series of amphiphilic triblock copolymers containing D-galactopyranose were synthesized by atom transfer radical polymerization (ATRP). The macroinitiator was prepared by the esterification between poly(ethylene glycol) monomethyl ether with a number-average molecular weight of 1200 g/mol (MeOPEO-1200) and 2-bromoisobutyryl bromide. The sugar-bearing monomer, 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPG) was polymerized using PMDETA/CuBr as catalytic system and anisol as solvent. The chemical structure and composition of the resultant polymer MeOPEO-b-PMAIPG were verified by 1H NMR. The molecular weights and their polydispersities were characterized by gel permeation chromatography (GPC). The results indicate that the polymerization follows the mechanism of ATRP. The amphiphilic copolymers can self-assembly to from micelles with PMAIPG as the core and PEO as the corona, which have potential applications as biomaterials or controlled release drug delivery systems.