Synthesis, spectral and thermal properties of homo- and copolymers of 2-[(5-methylisoxazol-3-yl)amino]-2-oxo-ethyl methacrylate with styrene and methyl methacrylate and determination of monomer reactivity ratios

The methacrylate monomer, 2-[(5-methylisoxazol-3-yl)amino]-2-oxo-ethyl methacrylate (IAOEMA), was synthesized by reacting 2-chloro-N-(5-methylisoxazol)acetamide dissolved in acetonitrile with sodium methacrylate in the presence of triethylbenzylammoniumchloride (TEBAC). The free-radical-initiated copolymerization of IAOEMA, with styrene (ST) and methyl methacrylate (MMA) was carried out in dimethylsulphoxide (DMSO) solution at 65 °C using 2,2^′-azobisisobutyronitrile (AIBN) as an initiator with different monomer-to-monomer ratios in the feed. The monomer (IAOEMA) and copolymers were characterized by FTIR, ¹H- and ¹³C-NMR spectral studies. The copolymer composition was evaluated by nitrogen content in polymers led to the determination of reactivity ratios. The reactivity ratios of the monomers were determined by the application of Fineman-Ross and Kelen-Tüdös methods. The analysis of reactivity ratios revealed that ST and MMA are more reactive than IAOEMA, and copolymers formed are statisticalle in nature. The molecular weights (M_w and M_n) and polydispersity index of the polymers were determined using gel permeation chromagtography. Glass transition temperatures of the copolymers were found to increase with an increase in the mole fraction of IAOEMA in the copolymers. The apparent thermal decomposition activation energies (E_d) were calculated by Ozawa method using the SETARAM Labsys TGA thermobalance.     

α，ω-二羧基-甲基丙烯酸丁酯低聚物的合成及MS分析

利用传统自由基聚合法，在四氢呋喃溶液中自由基引发聚合甲基丙烯酸丁酯单体而得到ω-羧基-甲基丙烯酸丁酯低聚物(CTBMA)(分子量在1500左右)；利用CTBMA末端酯基的反应特性，在二氧六环／水／KOH混合溶液中皂化CTBMA，使之转化为α，ω-羧基甲基丙烯酸丁酯低聚物(di-CTBMA)；研究了溶剂的类别、反应时间等反应条件对皂化产物结构的影响；利用MALDI-TOF-MS及LSIMS对皂化各阶段产物进行了分析监测．实验表明，在适当的皂化条件下，CTBMA皂化时主要为末端酯基转化为羧基，相应得到的产物di-CTMBA具有很好的结构特性，其官能团度(functionality)接近2．     

Addition of dipropylamine to multiacrylate and its model compound catalyzed by lithium dipropylamide

The nucleophilic addition reaction of dipropylamine to vinyl groups of multiacrylate - poly(2-acryloyloxyethyl methacrylate) and to 2-butyrylethyl acrylate as model compound has been investigated. Based on the results obtained, it has been shown that the addition reaction rate of dipropylamine to multiacrylate and 2-butyrylethyl acrylate is proportional to [CH₂=CH-] and to [(C₃H₇)₂NLi] with the ratio [(C₃H₇)₂NH]_o/[(C₃H₇)₂NLi]_o = 20. Second-order addition reaction rate constants and activation energies for the systems under investigation have been determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Unsymmetrically substituted ethane as a new and efficient initiator for the polymerization of methyl methacrylate and styrene

In this paper, we present a compound, 2,3-diphenyl butyronitrile (DPBN), which can be used as a new and efficient radical initiator for the polymerization of methyl methacrylate (MMA) and styrene (St). Very different from other compounds as a carbon-carbon initiator, DPBN is an unsymmetrically substituted ethane and works with high initiation reactivity at lower temperatures. This new compound as an initiator exhibits various advantages, such as easy preparation, high initiation reactivity, safe use and storage, and convenient handling.     

Thermoresponsive hydrophobic copolymer grafted on agar microspheres for all‐aqueous bioseparations

Agar microspheres were prepared by water–oil emulsification and cross‐linked under alkaline condition. The thermoresponsive hydrophobic copolymer, poly(N‐isopropylacrylamide‐co‐lauryl methacrylate‐co‐acrylamide), was grafted on the agar microspheres via atom transfer radical polymerization. The agar microspheres grafted with copolymers were characterized by light microphotography, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The chain lengths and hydrophobic monomer ratio of the grafting linear polymer had significant effects on the hydrophobicity and adsorption capacity of agar microspheres at different temperatures. The thermoresponsive microspheres were used for separation of proteins and showed binding and release behavior by change of temperatures without change in mobile phase composition. Thus, we suggest thermoresponsive agar microspheres as an alternative separation media for all‐aqueous bioseparations.     

含碘聚甲基丙烯酸酯类X光显影材料的制备

由甲基丙烯酸正丁酯（BMA）与2-(2'-碘苯甲酰)-O-甲基丙烯酸乙酯(2-IEMA)自由基共聚制备了一种X光显影材料。1H NMR分析表明,该共聚物中2种结构单元之比与投料比吻合。GPC测得该共聚物的分子量随2-IEMA含量增加而降低。DSC分析表明,共聚物的玻璃化转变温度在22.3~28.0 ℃之间,与Fox方程计算值比较接近,而且随2-IEMA含量的增加而升高。TGA测得共聚物的分解温度为250 ℃,具有很好的热稳定性。力学性能测试结果表明,共聚物的拉伸强度随BMA含量的增加而增加,最大拉伸强度可达到7.46 MPa。X光显影性测试表明,该共聚物具有良好的显影性,显影效果随2-IEMA含量增加而增强。     

Comparison on photo-initiators for the preparation of methacrylate monolithic columns for capillary electrochromatography

The synthesis of lauryl methacrylate monoliths for capillary electrochromatography by UV polymerization using several free-radical initiators (α,α′-azobisisobutyronitrile, 2,2-dimethoxy-2-phenylacetophenone, dibenzoyl peroxide (BPO) and lauroyl peroxide (LPO)) has been investigated. Using a 1,4-butanediol/1-propanol mixture as porogenic solvent, the influence of each initiator and its content on the morphological and electrochromatographical properties of beds was evaluated. Under their respective optimum content, satisfactory separations of a test mixture of PAHs with similar efficiencies (minimum plate heights of 8.0–12.7 μm obtained from Van Deemter plots) were achieved for the four investigated photo-initiators. The columns photo-polymerized with LPO provided the best compromise between chromatographic performance and analysis time. Moreover, this initiator showed a fine control in the column retention properties. The resulting monolithic columns exhibited a good run-to-run repeatability in the tested chromatographic parameters (RSD < 2.4%) for all initiators investigated; and satisfactory column-to-column repeatability (RSD < 6.0%), except for beds photo-polymerized with BPO (RSD < 10.8%).     

Isothermal titration calorimetric studies of surfactant interactions with negatively charged, ‘hairy’ latex nanoparticles

Isothermal titration calorimetry (ITC) measurements of the mixture of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) with negatively charged, hairy copolymer latices (poly-(2,3-epoxypropylmethacrylate-co-methacrylic acid) in different ratio) at high water excess indicate a monomer adsorption mechanism of CTAB by the polymer particles. The number of adsorbed CTAB molecules at saturation corresponds approximately to the number of negative elementary charges bound at the surface of the latices. The mixing enthalpy is the sum of demicellization and sorption enthalpies. At 25 °C for CTAB the demicellization enthalpy amounts to 10 kJ/mol, whereas the adsorption enthalpy varies from –7 kJ/mol (surface charge density of the latices =–0.37 C/m²) to +3 kJ/mol (=–0.085 C/m²). The hydrodynamic radius R_H of the latex particles upon titration of cationic detergent and salt (NaBr) decreases by about 2 nm until the onset of aggregation near the isoelectric point. Titration of nonionic or anionic detergents has much less influence on the hydrodynamic radius and produces no measurable adsorption heat. The results are consistent within a model of latex particles with extended negatively charged polymer chains interacting predominantly via Coulombic forces with detergents.     

Methacrylate modified clays and their polystyrene and poly(methyl methacrylate) nanocomposites

Two methacrylate‐modified clays have been prepared and used to produce nanocomposites of polystyrene and poly(methyl methacrylate) by in situ polymerization. These nanocomposites have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cone calorimetry and the evaluation of mechanical properties. When the clay contains only a single methacrylate unit, the styrene system is exfoliated but methacrylate is intercalated. When two methacrylate units are present on the cation of the clay, both systems are exfoliated. TGA data show that the thermal stability of all the nanocomposites is improved, as expected. The relationships between the fire properties and nanostructure of the nanocomposites are complicated, as shown by cone calorimetry. The conclusions that one may reach using cone calorimetry do not completely agree with those from XRD and TEM. The evaluation of mechanical properties shows an increase in Young's modulus for all nanocomposites along with a decrease in elongation; tensile strength is decreased for methacrylate nanocomposites but increased for styrenics systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Reactions of poly(methyl methacrylate) radicals with some <Emphasis Type="Italic">p</Emphasis>-quinones in the presence of tri-<Emphasis Type="Italic">n</Emphasis>-butylboron in methyl methacrylate polymerization

The polymerization of methyl methacrylate initiated by dicyclohexyl peroxydicarbonate at 30 °C was studied in the presence of tri-n-butylboron and a series of quinones, namely, p-benzoquinone, chloranil, and 2,5-di-tert-butyl-p-benzoquinone, whose concentration changed from 0.25 to 2.00 mol.%. The initial polymerization rate and molecular weight of poly(methyl methacrylate) depend on the structure and concentration of quinone. The growth radicals react with p-benzoquinone and chloranil predominantly at the C=C bond, while they react at the C=O bond of 2,5-di-tert-butyl-p-benzoquinone. The terminal stable oxygen-centered radicals that formed react with alkylborane, terminating reaction chains and generating alkyl radicals into the bulk. The latter are involved in chain initiation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2114–2119, October, 2004.