Thermoresponsive random copolymers based on 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEG8‐9MA) are synthesized by atom transfer radical polymerization (ATRP). In a second step, they are used as macroinitiators for the ATRP of glycidyl methacrylate (GMA), introducing a short end‐block with epoxy functionalities that allows the connection of the thermoresponsive polymers to a variety of molecules, surfaces, or particles. The resulting epoxy functionalized terpolymers exhibit lower critical solution temperatures (LCST), which can be adjusted by changing the feed monomer ratio of MEO2MA and OEG8‐9MA. Binary blends show one or two cloud points depending on the blend composition. A model for the polymer collapse in one mixed particle or in two different particles as function of composition is proposed.
A new hyper-branched surface in which three species of architectures were constructed as stem chain, branched stem and twig chain-grafted branched chain of poly(poly(ethylene glycol)methacrylate) (poly(PEGMA)) by photo-polymerization using dithiocarbamyl group (DC) as iniferter was prepared and characterized. For these surfaces, radical copolymerization of styrene and an iniferter-activated chain that was previously synthesized was performed for using as base materials for surface coating. On a DC-activated surface, hyper-branched poly(PEGMA) was introduced by photo-polymerization and dithiocarbamylation. All modified surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Our results demonstrated that a highly hyper-branched graft architecture of poly(PEGMA) can be constructed on PU surface by photo-polymerization using dithiocarbamyl group as iniferter, in which first, second and third generation gave stem chain, branched chain and twig chain of poly(PEGMA), respectively. Our hyper-branched surfaces could be regulated by photo-irradiation time and might be controlled by feed amounts or other reaction conditions. This highly dense architecture of PEG chain with hydrophilicity and chain mobility, grafted on surface, is expected to be effectively utilized in bio-implantable substrates or micro- or nano-patterned surfaces for immobilization of bioactive molecules in biomedical fields. 相似文献
With fac‐Ir(ppy)3 as photoredox catalyst and ethyl 2‐bromoisobutyrate (EBiB) as initiator, the homopolymerization of methyl methacrylate (MMA) in different solvents, such as N,N‐dimethylformamide (DMF), acetonitrile, and anisole are run under irradiation of an LED lamp. The results show that anisole is a better solvent for the polymerization with regard to the polydispersity index (PDI). A well‐controlled polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) is demonstrated and the clean block copolymer of PMMA‐b‐PPEGMA is prepared with PDI less than 1.3; however, the 2‐(dimethylamino) ethyl methacrylate (DMAEMA) polymerization is poorly controlled. With the PMMA as macromolecular initiator, the block copolymer PMMA‐b‐PDMAEMA can be prepared with PDI around 2.0.
We report on the synthesis and self‐assembly of a novel well‐defined coil‐brush diblock copolymer with linear crystalline polyethylene (PE) as the coil block and hydrophilic poly [oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) as rod brush via a combination of chain shuttling ethylene polymerization (CSEP) and atom transfer radical polymerization (ATRP). Initially, bromine end‐terminated PE macroinitiator (PE–Br) was synthesized through the esterification of 2‐bromo‐2‐methylpropionyl bromide with monohydroxyl‐terminated PE (PE–OH) which was prepared by means of CSEP with 2,6‐bis[1‐(2,6‐dimethylphenyl)imino ethyl] pyridine iron (II) dichloride/methylaluminoxane (MAO)/ZnEt2 and subsequent in situ oxidation with oxygen. The resultant PE‐b‐POEGMA coil‐brush diblock copolymer was synthesized by ATRP of monomethoxy‐capped oligo(ethylene glycol)methacrylate (OEGMA) using PE–Br as macroinitiator. The self‐assembly of the double‐crystalline PE‐b‐POEGMA in aqueous solution was investigated by dynamic light scattering, transmission electron microscopy and cryofield emission scanning electron microscopy. It was found that, in water, a solvent selectively good for the POEGMA brush, PE‐b‐POEGMA chains could self‐assemble to form sandwich‐like micelles with the insoluble and crystallized PE blocks as the interlayer cores and the soluble and swollen POEGMA brush as the outer‐layer shell. The crystallization of both PE and POEGMA blocks in self‐assembled structure formed from aqueous solution was investigated by differential scanning calorimetry.
The fracture energy required to separate layers of hydrogel films was investigated to evaluate the impact of bulk polymer diffusion on hydrogel/hydrogel adhesion and to obtain molecular information on the fracture energy in polymer mucoadhesion. Poly(ethylene glycol) (PEG) was incorporated in a hydrogel and was used as an adhesion promoter. The influence of PEG molecular weight and contact time on PEG diffusion across the hydrogel/hydrogel interface was investigated by using tensiometric studies and near-field FTIR microscopy. These experiments indicated that linear PEG diffusion enhanced the adhesion between the two hydrogel layers. The enhanced adhesion could not be explained by surface wetting phenomena alone. These results indicated that bulk diffusion of linear polymers such as PEG (adhesion promoter) incorporated into polymer networks (hydrogels) was an effective technique for enhancing gel/gel adhesion in various applications including polymer/mucus interactions in mucoadhesion and development of mucoadhesive controlled drug delivery systems. 相似文献
Upper critical solution temperature (UCST)‐type thermoresponsive behavior of poly(ethylene glycol)–poly(acrylic acid) (PEG–PAA) and poly(poly(ethylene glycol) methacrylate)–poly(acrylic acid) (PPEGMA–PAA) interpolymer complexes has been observed in isopropanol. For these investigations, PPEGMA and PAA with various average molecular weights have been synthesized by atom transfer radical polymerization. It has been found that both the PEG and PPEGMA have lower cloud point temperatures (T cp) than its mixed polymer solutions with PAA, whereas PAA does not show such behavior in the investigated temperature range. These findings indicate the reversible formation of interpolymer complexes with variable structure and composition in the solutions of the polymer mixtures in isopropanol. Increasing the ethylene glycol/acrylic acid molar ratio or the molecular weight of either the PAA or the H‐acceptor PEG component of the interpolymer complexes increases the UCST‐type cloud point temperatures of these interpolymer systems. The polymer–polymer interactions by hydrogen bonds between PAA and PEG or PPEGMA and the correlations between T cp and structural parameters of the components revealed in the course of these investigations may be utilized for exploring well‐defined UCST‐type material systems for various applications.
AbstractA thermo- and pH-sensitive hydrogel was prepared by a facile free aqueous radical copolymerization of PEGMA and AAc without any crosslinkers for controlled drug delivery. The successful fabrication of hydrogels was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA) measurements. The morphological, mechanical and swelling properties of the obtained hydrogels were studied systematically. The results showed that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the content of AAc. Moreover, the obtained hydrogels showed an excellent thermo-, pH- and salinity sensitivities. Release profiles of 5-Fu were studied at different pH (gastric pH 1.2 and intestinal pH 7.4) and temperatures (25?°C and 37?°C). The results showed that the release is very low at pH 1.2/37?°C and high at pH 7.4/25?°C. The cytotoxicity of hydrogels to cells was determined by an MTT assay. The result demonstrated that the blank hydrogels had negligible toxicity to cells, whereas the 5-Fu-loaded hydrogels remained high in cytotoxicity for LO2 and HepG-2 cells. Results of the present investigation exemplify the potential of this novel thermo- and pH-sensitive hydrogel for the controlled and targeted delivery of the anti cancer drug 5-Fu. 相似文献
Cellular interaction and platelet adsorption were investigated on poly(ethylene oxide) (PEO) immobilized silicone rubber membrane (SR) which has polyacrylic acid grafts on the surfaces. Polyacrylic acid (PAA) had been introduced to the SR surface after Ar plasma treatment of SR surfaces to introduce peroxide groups. Surface characterizations were made using ATR-FTIR, ESCA, SEM, and contact angle measurements. Experimental results obtained by ESCA high resolution curve fitting spectra indicated that the amount of bisamino PEO of different molecular weights immobilized onto SR surfaces were similar, which showed that the influence of the length of molecular chains (-C-C-O-) on the reactivity of terminal amino group is negligible. The wettability of modified SR surfaces increased with an increase in PEO molecular weight. Biological studies such as corneal epithelial cell culture and blood platelet adhesion were performed to understand the biocompatibility of modified SR surfaces. Biological studies using corneal epithelial cells showed that cell migration, attachment and proliferation onto PEO-20000 immobilized SR surface were suppressed, whereas these biological activities on PEO-600 were enhanced. Another study on platelet adhesion revealed that many platelets attached to PEO-600 immobilized SR, while platelet deposition was rarely observed on SR grafted with PEO-3350. The effects of different PEO molecular chains on biological response were discussed. 相似文献
Ethyl cellulose‐graft‐poly(2‐hydroxyethyl methacrylate) (EC‐graft‐PHEMA) graft copolymers were synthesized by atom‐transfer radical polymerization (ATRP) in methanol. The graft copolymers were characterized by means of gel‐permeation chromatography (GPC) and 1H NMR spectroscopy. The kinetic study indicated that the polymerization was controllable. The EC‐graft‐PHEMA copolymers self‐assembled in water into spherical micelles. The morphology of the micelles was characterized by dynamic light scattering (DLS) and transmission electric microscopy (TEM) and the formation process of the micelles was discussed.
