Side‐chain crystallization behavior of graft copolymers consisting of an amorphous main chain and crystalline side chains. II. Poly(n‐hexyl methacrylate)‐graft‐poly(ethylene glycol)

The phase behavior and crystallization of graft copolymers consisting of poly(n‐hexyl methacrylate) (PHMA) as an amorphous main chain and poly(ethylene glycol) (PEG) as crystallizable side chains (HMAx with 15 ≤ x ≤ 73, where x represents the weight percentage of PEG) were investigated. Small‐angle X‐ray scattering profiles measured above the melting temperature of PEG suggested that a microdomain structure with segregated PHMA and PEG domains was formed in HMA40 and HMA46. This phase behavior was qualitatively described by a calculated phase diagram based on the mean‐field theory. Because of the segregation of PEG into microdomains, the crystallization temperature of the PEG side chains in HMAx was higher than that in poly(methyl acrylate)‐graft‐poly(ethylene glycol) having a similar value of x, which was considered to be in a disordered state above the melting temperature. In HMAx with x ≤ 40, PEG crystallization was strongly restricted, probably because the PEG microdomains were isolated in the PHMA matrix. As a result, the growth of PEG spherulite was not observed because the PEG crystallization occurred after vitrification of the PHMA segregated domains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 129–137, 2007     

Synthesis and characterization of functional gradient copolymers of allyl methacrylate and butyl acrylate

Functional spontaneous gradient copolymers of allyl methacrylate (A) and butyl acrylate (B) were synthesized via atom transfer radical polymerization. The copolymerization reactions were carried out in toluene solutions at 100 °C with methyl 2‐bromopropionate as the initiator and copper bromide with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Different aspects of the statistical reaction copolymerizations, such as the kinetic behavior, crosslinking density, and gel fraction, were studied. The gel data were compared with Flory's gelation theory, and the sol fractions of the synthesized copolymers were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The copolymer composition, demonstrating the gradient character of the copolymers, and the microstructure were analyzed. The experimental data agreed well with data calculated with the Mayo–Lewis terminal model and Bernoullian statistics, with monomer reactivity ratios of 2.58 ± 0.37 and 0.51 ± 0.05 for A and B, respectively, an isotacticity parameter for A of 0.24, and a coisotacticity parameter of 0.33. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5304–5315, 2006     

Copolymerization of N‐vinylcaprolactam and glycidyl methacrylate: Reactivity ratio and composition control

Free‐radical copolymerizations of N‐vinylcaprolactam (VCL) and glycidyl methacrylate (GMA) were investigated to synthesize temperature‐responsive reactive copolymers with minimized compositional heterogeneity. The average copolymer composition was determined by Fourier transform infrared and nuclear magnetic resonance techniques. The reactivity ratios for VCL and GMA were found to be 0.0365 ± 0.0009 and 6.44 ± 0.36 by the Fineman–Ross method and 0.039 ± 0.006 and 6.75 ± 0.29 by the Kelen–Tudos method, respectively. When prepared by batch polymerization, VCL–GMA copolymers had a highly heterogeneous composition and fractions of different solubilities in water. The use of a gradual feeding technique, which included the sequential addition of more reactive GMA monomer into the reaction, yielded copolymers with much more homogeneous composition. The produced copolymers with 0.9 and 0.11 fractional GMA contents preserved their temperature‐responsive properties and precipitated from aqueous solutions when the temperature exceeded 31 °C. The GMA units in the VCL–GMA copolymers were capable of reacting with amino end‐functionalized poly(ethylene oxide) at room temperature to produce poly(N‐vinylcaprolactam)–poly(ethylene oxide) graft copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 183–191, 2006     

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (M_n) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured M_n's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr₂) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]₀/[methyl α‐bromoisobutyrate]₀/[CuBr]₀/[CuBr₂]₀/[Me₆TREN]₀ = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of Cu^IBr/Me₆TREN in HFIP, there were [Cu(Me₆TREN)Br]⁺ and [Cu(Me₆TREN)OCH(CF₃)₂]⁺, indicating that HFIP should coordinate to the Cu^I/Me₆TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006     

甲基丙烯酸全氟烷基代乙酯对天然橡胶乳液辐射改性研究

天然橡胶的性能与其组成中的C C双键有密切关系,由于C C双键的存在,为天然橡胶的改性提供了便利,大多数天然橡胶的改性方法,如氯化、氢氯化、环化、环氧化、接枝共聚等皆是建立在这一思路基础上的.White等[1]认为接枝天然橡胶的目的是提高天然橡胶的机械强度,赋予特殊的功能.作     

乙烯系单体自由基聚合的阻聚效应——Ⅸ.受阻胺-醌类电荷转移络合物对甲基丙烯酸甲酯自由基聚合的阻聚及历程

用膨胀计法研究了西氯苯醌(CA)、苯醌(BQ)与受阻胺二异丙胺(DIPA)、2,2,6,6-四甲基-4-羟基哌啶(TMP)形成的电荷转移络合物(CTC)对偶氮二异丁腈(AIBN)引发的甲基丙烯酸甲酯(MMA)自由基聚合阻聚效应。结果表明,CA-DIPA、CA-TMP、BQ-DIPA和BQ-TMP对MMA的自由基聚合均产生较单独的醌或胺更显著的阻聚能力。其中以CA-DIPA阻聚效果更佳。比较了MMA在苯或乙腈中的溶液聚合,得类似结果。初步讨论了受阻胺-醌电荷转移络合物对MMA自由基聚合的阻聚反应机理。     

Elimination of matrix effects for headspace solid-phase microextraction of important volatile compounds in red wine using a novel coating

In this paper, hydroxy-terminated silicone oil-butyl methacrylate-divinylbenzene (OH-TSO-BMA-DVB) copolymer was first synthesized and used as stationary phase with the aid of γ-methacryloxypropyltrimethoxylsilane (KH-570) as bridge in solid-phase microextraction (SPME) using sol–gel method and cross-linking technique. It has high extraction efficiency for both polar alcohols and fatty acids and nonpolar esters in comparison with commercial PDMS, PDMS-DVB and PA fibers. A simple and sensitive headspace SPME-gas chromatography (HS-SPME-GC) method using the novel fiber was presented for the simultaneous analysis of both polar alcohols and fatty acids and nonpolar esters in wine. To check the matrix effects, various model wine matrices, including distilled water; 11.5% ethanol/water (v/v) solution; a concentrated synthetic wine; a ‘volatile-free’ wine and a real wine were investigated in detail. Matrix effects were compensated for by using internal standard method and selecting the ‘volatile-free’ wine as working standard. The method presented in this study showed satisfactory linearity, precision, detection limits and accuracy. The recoveries obtained ranged from 85.87 to 104.2%, and the relative standard deviation values were below 9%. The results obtained indicated that the present method is a validated and accurate procedure for the simultaneous determination of both polar and nonpolar aroma compounds in wine.     

掺C60有机玻璃的吸收光谱研究

研究了Ｃ６０分别在有机玻璃（ＰＭＭＡ）和正己烷中的吸收光谱，发现Ｃ６０在有机玻璃中的吸收峰同在正己烷中相互对应，同时前者的吸收峰相对于后者峰宽变大，峰位产生红移，分析了产生这种现象的原因。     

Preparation of HPMC–EA–DMAEMA nanosized latex

Nanosized copolymer latex of hydroxypropylmethylcellulose (HPMC) grafted with ethyl acrylate (EA) and dimethylaminoethyl methacrylate (DMAEMA) has been prepared by acidifying submicron-sized latex particles synthesized by soap-free emulsion graft copolymerization using potassium persulfate (KPS) as initiator. The effects on the diameter of the latex particles of different conditions, for example concentration of DMAEMA, amount of HPMC, and ratio of HCl to DMAEMA for acidification, were investigated. It was found that increasing the mole ratio of HCl to DMAEMA to 1.0 and increasing the DMAEMA content both resulted in a decrease in particle diameter, whereas increasing the amount of HPMC resulted in larger particle sizes. Measurement by dynamic light scattering (DLS) revealed the diameter of the latex particles was >200 nm before acidification and <100 nm after acidification. Evidence of grafting was obtained by use of Fourier transform infrared (FTIR) spectroscopy. Transmission electron microscopy (TEM) was used to characterize the morphology of the copolymer particles before and after acidification.