聚天冬氨酸的合成研究

以L-天冬氨酸为原料,磷酸为催化剂,在不同溶剂中进行缩聚反应,合成中间体聚丁二酰亚胺(PSI),当混合溶剂为m三甲苯／m环丁砜=7／3时,可得到较高分子量的PSI。当催化剂与单体的质量比为0．14时,分子量达到最大值。将PSI碱解得到聚天冬氨酸。     

Copolymerization of 2,3-Dihydropyran and Ethyl Vinyl Ether with Maleic Anhydride

2,3-Dihydropyran (DHP) and ethyl vinyl ether (EVE) were co-polymerized with maleic anhydride (MA) with benzoyl peroxide at 60°C, and 1:1 alternating copolymers were obtained. The rates were maximum at 1:1 monomer composition. Spontaneous copolymerization and solvent effect on the rate were observed in the copolymerization of DHP with MA, in which initial rates were slower in more polar solvents. Participation of charge transfer complex was considered. EVE copolymerized rapidly with MA, reaching the theoretical limiting conversion of 1:1 alternating copolymerization. Although DHP-MA comonomer pair and EVE-MA comonomer pair formed similar 1:1 charge transfer complexes, DHP copolymerized slowly with MA to produce a low molecular weight copolymer, and the limiting conversion was much lower than the theoretical one. To explain these, degradative chain transfer to DHP monomer is proposed as the initial rate of DHP-MA copolymerization is proportional to the initiator concentration to the power 1.1. Q and e values of DHP were calculated to be 0.013 and -0.93, respectively, from the monomer reactivity ratios of copolymerization of DHP with acrylonitrile [r₁ (DHP)=0.003 ± 0.006 and r₂ (AN)=3.6 ± 0.3].     

Synthesis of poly(succinimide) by bulk polycondensation of L‐aspartic acid with an acid catalyst

The bulk polycondensation of L ‐aspartic acid (ASP) with an acid catalyst under batch and continuous conditions was established as a preparative method for producing poly(succinimide) (PSI). Although sulfuric acid, p‐toluenesulfonic acid, and methanesulfonic acid were effective at producing PSI in a high conversion of ASP, o‐phosphoric acid was the most suitable catalyst for yielding PSI with a high weight‐average molecular weight (M_w) in a quantitative conversion; that is, the M_w value was 24,000. For the continuous process using a twin‐screw extruder at 3.0 kg · h⁻¹ of the ASP feed rate, the conversion was greater than 99%, and the M_w value was 23,000 for the polycondensation with 10 wt % o‐phosphoric acid at 260°C. Sodium polyaspartate (PASP‐Na) originating from the acid‐catalyzed polycondensation exhibited high biodegradability and calcium‐ion‐chelating ability. The total organic carbon value was 86 ∼ 88%, and 100 g of PASP‐Na chelated with 5.5 ∼ 5.6 g of calcium ion, which was similar to the value for PASP‐Na from the acid‐catalyzed polycondensation with a mixed solvent © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 117–122, 2000     

Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi‐batch reaction and compared with the experimental results.

     

Poly(lactic acid) Synthesis in Solution Polymerization

The step-growth polymerization of L-lactic acid in solution was studied in this work. In order to attain a polymer with high molecular weight, the water formed during the polymerization must be continuously removed. The use of organic solvents with high boiling point, drying agents and reduced pressure led to poly(lactic acid) (PLA) with high molecular weight, directly from the monomer. Tin (II) chloride dihydrate, SnCl₂.2H₂O, was the best of the catalysts tested as it allowed achieving PLA with a molecular weight close to 80 000 g.mol⁻¹. However, the stereoregurarity control is a severe problem in PLA synthesis by step-growth due to transesterification reactions, which lead to an inversion of the conformation and a decrease of the optical purity of the polymer. Specific rotation measurements were used in this work and showed to be a powerful technique to evaluate the racemization extent. The thermal stability of the PLA samples was evaluated by DSC which exhibits a thermal behaviour similar to the commercial Polylactide.     

Importance of Radical Transfer in Precipitation Polymerization: The Case of Vinyl Chloride Suspension Polymerization

The importance of radical transfer between the reactive phases in precipitation polymerization processes is investigated with the vinyl chloride suspension polymerization as an example. A two‐film model that accounts for a mass transfer resistance in both the monomer‐rich and the polymer‐rich phase is constructed and applied. Equilibrium is assumed at the interphase boundary. Based on model calculations using intrinsic rate coefficients obtained by regression to experimental data the effect of accounting for radical transfer between the reactive phases on the simulated monomer conversion and total moments of the molar mass distribution is demonstrated. It is found that the effect of radical transfer between the reactive phases is most pronounced at low polymerization temperatures.

     

Cobalt‐Mediated Radical Polymerization of Vinyl Acetate and Acrylonitrile in Supercritical Carbon Dioxide

Cobalt‐mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO₂). CMRP of VAc is conducted using an alkyl‐cobalt(III) adduct that is soluble in scCO₂. Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass (M_n) are key parameters that affect the CMRP in scCO₂. It is noticed that CMRP is controlled for M_n up to 10 000 g mol⁻¹, but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO₂, is then successfully used to initiate the acrylonitrile polymerization. PVAc‐b‐PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO₂ without the utilization of fluorinated comonomers or organic solvents.

     

Synthesis and characterization of biodegradable poly(L-aspartic acid-co-PEG)

The melt polycondensation reaction of the prepolymer prepared from N-(benzyloxycarbonyl)-L -aspartic acid anhydride (N-CBz-L -aspartic acid anhydride) and low molecular weight poly(ethylene glycol) (PEG) using titanium isopropoxide (TIP) as a catalyst produced the new biodegradable poly(L -aspartic acid-co-PEG). This new copolymer had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the preparation of the prepolymer were obtained by using a 0.12 mol % of p-toluenesulfonic acid with PEG 200 for 48 h. The weight-average molecular weight of the prepolymer increased from 1,290 to 31,700 upon melt polycondensation for 6 h at 130°C under vacuum using 0.5 wt % TIP as a catalyst. The synthesized monomer, prepolymer, and copolymer were characterized by FTIR, ¹H- and ¹³C-NMR, and UV spectrophotometers. Thermal properties of the prepolymer and the protected copolymer were measured by DSC. The glass transition temperature (T_g) of the prepolymer shifted to a significantly higher temperature with increasing molecular weight via melt polycondensation reaction, and no melting temperature was observed. The in vitro hydrolytic degradation of these poly(L -aspartic acid-co-PEG) was measured in terms of molecular weight loss at different times and pHs at 37°C. This pH-dependent molecular weight loss was due to a simple hydrolysis of the backbone ester linkages and was characterized by more rapid rates of hydrolysis at an alkaline pH. These new biodegradable poly(L -aspartic acid-co-PEG)s may have potential applications in the biomedical field. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2949–2959, 1998     

甲基取代聚芳醚酮的合成与表征

甲基取代聚芳醚酮的合成与表征;甲基侧基;缩聚;热性能     

衰减链转移(DT)聚合醋酸乙烯酯的动力学

在醋酸乙烯酯的普通自由基聚合体系中加入少量碘（质量分数为0.57%～0.86%）,用偶氮二异丁腈作引发剂合成聚醋酸乙烯酯,对其聚合反应的动力学及反应机理进行了研究。 考察了碘质量分数对聚合反应速率、聚合物分子量及分子量分布的影响,发现随着碘浓度的增加,聚合物分子量及分子量分布得到更好的控制;对聚合过程进行了核磁跟踪,考察了聚合过程中几种化合物的变化情况,特别是初级自由基与碘生成的加合物A-I（A来自引发剂分裂后产生的自由基）及单体加合物A-Mn-I（M代表单体单元）的变化情况;对聚合物结构作了详细的1H NMR分析,结果表明,聚合过程中分子量随时间延长而逐渐增大,分子量分布随单体转化率增加而变窄,聚合终期,单体转化率达到80%左右时,所得聚合物分子量分布窄（Mw/Mn≤1.41）,且含有碘端基。该方法的自由基聚合具有活性/可控的性质。     

Synthesis of poly(aryl ether ketone)s containing diphenyl moieties by electrophilic Friedel–Crafts solution polycondensation

A new monomer, 4,4′‐bis(4‐phenoxybenzoyl)diphenyl (BPOBDP), was prepared by Friedel–Crafts reaction of 4‐bromobenzoyl chloride and diphenyl, followed by condensation with potassium phenoxide. Novel poly(ether ketone ketone) (PEKK)/poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) copolymers were synthesized by electrophilic Friedel–Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of diphenyl ether (DPE) and BPOBDP, in the presence of anhydrous aluminum chloride and N‐methyl‐pyrrolidone (NMP) in 1,2‐dichloroethane (DCE). The copolymers obtained were characterized by various analytical techniques such as FT‐IR, DSC, TGA, and wide‐angle X‐ray diffraction (WAXD). The results showed that the resulting copolymers exhibited excellent thermal stability due to the existence of diphenyl moieties in the main chain. The glass transition temperatures are above 152°C, the melting temperatures are above 276°C, and the temperatures at a 5% weight loss are above 548°C in nitrogen. The copolymers with 50–70 mol% BPOBDP had tensile strengths of 101.5–102.7 MPa, Young's moduli of 3.23–3.41 GPa, and elongations at break of 12–17%. All these copolymers were semicrystalline and insoluble in organic solvents. Copyright © 2008 John Wiley & Sons, Ltd.     

Phase Equilibria in the Systems Oxolane + Vinyl Acetate,Oxolane + Ethyl 1,1-Dimethylethyl Ether and Vinyl Acetate + Ethyl 1,1-Dimethylethyl Ether

Abstract

Vapor-liquid equilibrium at 94kPa has been determined for the binary systems oxolane (THF) + vinyl acetate, oxolane + ethyl 1,1-dimethylethyl ether (ETBE) and vinyl acetate + ethyl 1,1-dimethylethyl ether. The three systems present slight to moderate positive deviations from ideal behavior and, to a first approximation, can be considered to behave like regular solutions. An azeotrope is present in the system vinyl acetate + ETBE that boils at 340.40 K and contains 49.8% mol vinyl acetate. The activity coefficients of the systems were correlated reasonable well with its composition by the Wohl, Wilson, UNIQUAC and NRTL models. The boiling points of the binary systems were correlated with the Wisniak-Tamir equation.     

Synthesis and characterization of multiblock copolyesters containing poly(dimethylsiloxane) in the soft segments

Synthesis and thermal properties of poly(aliphatic/aromatic-ester) copolymers containing additionally poly(dimethylsiloxane) (PDMS) chains in the soft segments are discussed. A two step method of transesterification and polycondensation from the melt was carried out in a presence of magnesium-titanate catalyst. An aliphatic dimer fatty acid was used as a component of the soft segments while poly(butylene terephthalate) (PBT) constituted the hard blocks. Effectiveness of the incorporation of PDMS into polymer chain was confirmed by the Soxhlet extraction and infrared spectroscopy of an excess of 1,4-butane diol destilled off from the polycondensation reaction. Multiblock copolymers showed microphase separation as determined by differential scanning calorimetry. Incorporation of a small amount of PDMS (up to 14.5 wt.-%) into polymer chain containg low concentration of hard segments of PBT lead to decrease in crystallinity of such copolymers. This may indicate that semicrystalline PBT are dissolved in the amorphous matrix of the soft segments.     

聚醚醚酮酮（PEEKK）和含联苯结构聚醚醚酮酮（PEBEKK）共聚物的SAXS研究

应用一维电子密度相关函数方法，对含不同联苯结构的ＰＥＥＫＫ－ＰＥＢＥＫＫ共聚物样品小角Ｘ射线散射（ＳＡＸＳ）去模糊强度分析计算表明：ＰＥＥＫＫ－ＰＥＢＥＫＫ共聚物的聚集态结构明显地依赖于共聚物中联苯含量。当联苯含量ｎｂ＝０．３５时，积分不变量Ｑ，长周期Ｌ，平均结晶片层厚ｄ，电子密度差η_ｃ－η_ａ和结晶度Ｗ_（ｃ，ｘ）值为最小，比表面积Ｏ_ｓ为最大。     

溶液法星型聚乳酸的合成与表征

探讨了采用辛酸亚锡为催化剂,多元醇及多元酸为引发剂,以溶液法制备星型聚乳酸的可行性,研究了不同引发剂对产物分子量的影响.采用核磁共振及DSC对产物进行了表征,结果表明:以溶液法合成星型聚乳酸是可行的,但与丙交酯开环聚合制备星型聚乳酸的方法相比,溶液法在产物结构和分子量控制上并不十分有效,由于反应受到多官能团核引发剂空间位阻和反应概率的影响,聚乳酸产物的结构除星型结构外也同时存在大量的线型结构.     

一种聚芳醚酮齐聚物的合成和晶体结构(英文)

合成了一种聚芳醚酮齐聚物 4 ,4′-双 (对氟苯甲酰基 )二苯醚 ,并以IR ,DSC ,13CNMR等技术对其进行了表征。运用多晶粉末X射线衍射方法 ,对其晶体结构进行了确定 ,其晶体结构为首次报道。     

Thermogravimetric Analysis of Vinyl Chloride/Acrylonitrile Copolymers

The dehydrohalogenation of several alternating and random vinyl chloride/acrylonitrile copolymers was characterized by thermogravimetry. The polymers were made in solution, and the conversions were kept below 5% to insure uniform sequence distributions. Hydrogen chloride was generated within a relatively narrow temperature range somewhere between 200 and 300°C depending on the sequence distribution, relative viscosity, and composition. The weight-loss during the dehydrohalogenation could be attributed completely to the hydrogen chloride available in the copolymer. Alternating copolymers were significantly more stable than random copolymers were significantly more stable than random copolymers at the same relative viscosity. For a given sequence distribution or composition, stability decreased with decreasing relative viscosity. The stability decreased as acrylonitrile content was increased from 23 to 57%.

The thermogravimetric analyzer was interfaced with a digital computer. The digitized data were smoothed and differentiated by convoluted integers. The differentiated data provided rates for a qualitative discussion of dehydrohalogenation kinetics.     

Synthesis and Characterization of Poly(Aryl Ether Ketone)Containing Phthalazinone and Naphthalene Moieties

Poly (aryl ether ketone)s (PAEKs) are one of the most important high performanceengineering thermoplastics, widely used in electronic, electric, aircraft and aerospaceindustries. ICI' PEEK has enjoyed much commercial success due to its high operatingtemperatUre and superior strength. It has a Tg of 143oC, a Tin of 334'C and it is quitesolvent resistant. There is a growing demand for new materials to meet increasedperformance requirementS in many areas. Thus there has been considerable r…     

Swelling kinetics of poly(aspartic acid)/poly(acrylic acid) semi‐interpenetrating polymer network hydrogels in urea solutions

Semi‐interpenetrating network (semi‐IPN) hydrogels, composed of poly(aspartic acid) (PAsp) and poly(acrylic acid) (PAAc) with various ratios of PAsp to AAc, were prepared. In this work, swelling kinetics was investigated through calculating some parameters. The swelling ratios were measured at room temperature, using urea solutions as liquids to be absorbed. Compared to in deionized water, the hydrogels showed larger swelling ratios in urea solutions, which might be attributed to the chemical composition of urea. The equilibrium swelling ratio could achieve 600 g/g, and the equilibrium urea/water contents were more than 0.99. The diffusion exponents were between 0.5 and 0.7, suggesting that the solvent transport into the hydrogel was dominated by both diffusion and relaxation controlled systems. Therefore, the PAsp/PAAc semi‐IPN hydrogels were appropriate to carry substances in a urea/water environment for pharmaceutical, agricultural, environmental, and biomedical applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 666–671, 2010