On oxygen diffusion in poly(methyl methacrylate) films

ESR spectroscopy has been used to follow the kinetics of decay of radicals produced by UV-radiation in PMMA films upon exposure to oxygen in the temperature range 160-210 K. In the same films and at the same conditions, decay kinetics of phenanthrene phosphorescence has been studied at 180-220 K. Both types of the experiments give the same values for diffusion coefficients of oxygen in PMMA. Thus, from the oxygen diffusion standpoint, the sites of the radical stabilization and phenanthrene molecule localization in the polymer matrix do not differ.     

Surface graft polymerization of glycidyl methacrylate onto polyethylene and the adhesion with epoxy resin

Surface graft polymerization of glycidyl methacrylate (GMA) was carried out onto a high- density polyethylene (PE) sheet pretreated with corona to introduce peroxides onto the PE surface. Graft polymerization of GMA was effected by UV irradiation of the coronatreated PE in the presence of monomer solution without the use of any photosensitizer. The graft layer was found by staining the PE cross section to localize in the surface region of PE. The physical change in the PE surface was characterized by scanning electron microscopy, while the chemical changes due to the GMA graft polymerization were assessed by the dynamic contact angle, FT-IR, and x-ray photoelectron spectroscopy (XPS) measurement. The peroxide formation by corona exposure was confirmed by the XPS measurement after derivatization with SO₂. The epoxy groups introduced onto the PE surface by the GMA graft polymerization were reactive with water (in the presence of HCI) and amines. The adhesion between the GMA-grafted PE and an epoxy resin was studied by means of a shear strength test method. The GMA-grafted PE exhibited strong interfacial adhesion with the epoxy resin, compared to the original and corona-treated PE. The adhesion strength of the GMA-grafted PE was nearly two times higher than that of the corona-treated PE. This strongly suggests that the enhanced adhesion between the surface-grafted PE and the epoxy resin is ascribed to covalent bonding of the epoxy groups on the GMA-grafted surface to the amines in the epoxy resin. © 1995 John Wiley & Sons, Inc.     

Robust isocratic liquid chromatographic separation of functional poly(methyl methacrylate)

The separation of telechelic poly(methyl methacrylate) (PMMA) prepolymers based on the number of end-groups under critical liquid chromatography (LC) conditions has been studied using a bare-silica column, which can interact with polar functional groups. The critical solvent compositions for non-functional, mono-functional and bi-functional PMMAs were determined in normal-phase LC using mixtures of acetonitrile and dichloromethane (DCM) of varying composition as the mobile phase. The telechelic prepolymers were successfully separated according to hydroxyl (OH) functionality (with zero, one, or two OH groups, respectively) under the critical conditions, in which fast (5 min), base-line separations were obtained independent of molecular weight. Changing the column temperature, flow rate, and mobile-phase composition within a certain range did not affect the functionality separation. Therefore this isocratic LC separation method is quite robust. Evaporative light-scattering detector (ELSD) calibration curves were used for the quantitative analysis of functional PMMA prepolymers.     

Synthesis and characterization of poly (2-vinylpridine)-b-poly (t-butyl methacrylate)

The synthesis of well defined and monodisperse (M_w/M_n ≤ 1.2) narrow molecular weight distribution poly (2-vinylpyridine)-poly (t-butyl methacrylate) (P2VP-PTBMA) AB block copolymers is carried out by initiation of 2-vinylpyridine polymerization by 1,1-diphenylhexyllithium in THF at-78°C, followed by addition of TBMA and termination at ?78°C using MeOH. The formation of the BAB block copolymer is carried out in a similar fashion except that 1,4-dilithio-1,1,4,4-tetraphenylbutane is used as initiator. The corresponding synthesis of P2VP-PMMA block copolymers is carried in a similar manner, except that 1-2 equivalents of TBMA is used to end-functionalize the living P2VP before the addition of MMA. Without the addition of TBMA, trimodal molecular weight distributions in P2VP-b-PMMA are obtained. All the block copolymers are characterized by Size Exclusion Chromatography (SEC), Nuclear Magnetic Resonance (NMR), and Differential Scanning Calorimetry (DSC). © 1994 John Wiley & Sons, Inc.     

Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres

~~Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres~~     

以环糊精为核的星形高分子合成及其温度、pH敏感性研究

以不同用量的氯乙酰氯与 β 环糊精反应 ,得到含有不同酰化度的氯乙酰化 β 环糊精 ,以此化合物为引发剂 ,采用原子转移自由基 (ATRP)引发甲基丙烯酸N ,N 二甲氨基乙酯 (DMAEMA)聚合 ,得到温度及pH敏感的以 β 环糊精为核的星形聚合物 .通过红外光谱、1 3C NMR、1 H NMR和氯元素滴定分析确定了酰化后的 β 环糊精的结构 ,并采用红外光谱、1 H NMR、元素分析、DSC表征了以 β 环糊精分子为核的星形聚甲基丙烯酸N ,N 二甲氨基乙酯的大分子结构 ,紫外光谱研究表明聚合物水溶液具有明显的温度和pH敏感性 .     

PREPARATION OF LOW MOLECULAR WEIGHT POLY（GLYCIDYL METHACRYLATE） BY PHOTOPOLYMERIZATION

Low molecular weight poly（glycidyl methacrylate）s （PGMAs） were prepared by photopolymerization in ethyl acetate, with benzophenone （BP） as photoinitiator, and triethylamine （TEA） as hydrogen donor. The existence of semipinacol dormant end groups in PGMA was confirmed by FT-IR and ^1H-NMR, and the content of the semipinacol dormant groups was determined quantitatively by ^1H-NMR measurement. The effects of various thctors, such as reaction time, BP concentration and monomer concentration on the synthesis of the polymers were investigated systematically. The molecular weights of the polymers were also investigated with GPC. It is shown that increasing BP concentration and decreasing irradiation time and monomer concentration led to a significant decrease of the molecular weights.     

Star poly(methyl methacrylate) with end‐functionalized arm chains by ruthenium‐catalyzed living radical polymerization

Star polymers with end‐functionalized arm chains (surface‐functionalized star polymers) were synthesized by the in situ linking reaction between ethylene glycol dimethacrylate (linking agent) and an α‐end‐functionalized linear living poly(methyl methacrylate) in RuCl₂(PPh₃)₃‐catalyzed living radical polymerization; the terminal on the surface functionalities included amides, alcohols, amines, and esters. The star polymers were obtained in high yields (75–90%) with initiating systems consisting of a functionalized 2‐chloro‐2‐phenylacetate or ‐acetamide [F? C(O)CHPhCl; F = nPrNH? , HOCH₂CH₂O? , Me₂NCH₂CH₂O? , or EtO? ; initiator] and n‐Bu₃N (additive). The yield was lower with a functionalized 2‐bromoisobutyrate [Me₂NCH₂CH₂OC(O)CMe₂Br] initiator or with Al(Oi‐Pr)₃ as an additive. Multi‐angle laser light scattering analysis showed that the star polymers had arm numbers of 10–100, radii of gyration of 6–23 nm, and weight‐average molecular weights of 1.3 × 10⁵ to 3.0 × 10⁶, which could be controlled by the molar ratio of the linking agent to the linear living polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1972–1982, 2002     

Studies on photocrosslinkable copolymers of 4-methacryloyloxyphenyl-3′,4′-dimethoxystyryl ketone and methyl methacrylate

Copolymers with various contents of 4-methacryloyloxyphenyl-3′,4′-dimethoxystyryl ketone (MPDSK) and methyl methacrylate (MMA) were prepared in methyl ethyl ketone solution using benzoyl peroxide as a free radical initiator at 70 °C. Characterization of the resulting polymers was done by UV, FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The copolymer compositions were determined by ¹H NMR analysis. The monomer reactivity ratios were calculated using linearisation methods such as Finemann-Ross (r₁ = 0.4283 and r₂ = 0.3050), Kelen-Tudos (r₁ = 0.4264 and r₂ = 0.2606), and extended Kelen-Tudos (r₁ = 0.4022 and r₂ = 0.2704) methods as well as by a non-linear error-in-variables model (EVM) method using the computer program RREVM (r₁ = 0.4066 and r₂ = 0.2802). The molecular weights ( and ) and the polydispersity index of the copolymers were determined by gel permeation chromatography. The thermal stability of the copolymers increases with increase in concentration of MPDSK. Glass transition temperatures were determined by differential scanning calorimeter under nitrogen atmosphere. The photoreactivity of the copolymers having pendant chalcone moieties was studied in chloroform solution.     

Synthesis and micelle formation of triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) in aqueous solution

Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with ¹H and ¹³C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant K_v for pyrene in the micelle and in aqueous solution was about 10⁵. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius R_h,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks.