壳聚糖与甲基丙烯酸羟乙酯接枝聚合反应的研究

为了改善壳聚糖的亲水性，本用硝酸铈铵为氧化还原引发剂，研究了不同聚合反应条件下，壳聚糖接枝甲基丙烯酸羧乙酯（HEMA）的反应规律，研究了反应时间、反应温度、引发剂浓度和单体浓度对接枝聚合反应的影响，得到了最佳反应条件。用元素分析法和红外光谱对产物进行了表征。用元素分析方法对接枝进行定量分析。     

聚乙烯醇/丙烯酰胺接枝共聚物水凝胶的制备及表征

背景：交联水凝胶主要是使大分子链形成网状结构,网固交联基质,这样所得的水凝胶力学性能和透明性相对较差。 目的：采用自由基聚合机制制备聚乙烯醇/丙烯酰胺接枝共聚物水凝胶。 方法：以聚乙烯醇分子作为主链,聚乙烯醇分子中羟基为接枝点,共价接入丙烯酰胺单体。考察反应温度、时间、单体用量和引发剂用量对产物接枝率的影响,通过红外光谱表征聚乙烯醇/丙烯酰胺接枝共聚物共聚物的化学结构。 结果与结论：接枝聚合反应最佳反应条件：引发剂浓度0.04 mol/L、丙烯酰胺/聚乙烯醇(侧羟基)摩尔比6∶1、在40 ℃条件下反应4 h。经过FTIR分析,确认丙烯酰胺与聚乙烯醇发生了聚合反应;经过平衡溶胀测试,分析了接枝聚合物与聚乙烯醇的溶胀率随温度的变化关系,进一步证实了接枝聚合反应的发生,验证了接枝聚乙烯醇/丙烯酰胺接枝共聚物具有明显的温敏性能。      

介入导管材料的表面紫外光接枝润滑改性

研究了用紫外光直接引发亲水性单体在聚氨酯 ( PU)表面进行接枝反应。以改善 PU表面的润滑性。实验测定了单体浓度对接枝密度、吸水率、摩擦系数的影响 ,对不同反应方法得到的结果进行了比较 ,找到了获得最佳润滑表面的条件 ,并对接枝聚合物的表面进行了扫描电镜 ( SEM)观察。实验结果表明 :接枝亲水性单体可大大地改善聚氨酯表面的润滑性     

聚甲基丙烯酸羟乙酯水凝胶人工晶状体材料的合成与性能

以甲基丙烯酸羟乙酯为原料,过硫酸铵/偏重亚硫酸钠为引发体系,二甲基丙烯酸三乙二醇酯为交联剂,采用溶液聚合法制备了聚甲基丙烯酸羟乙酯水凝胶(PHEMA)人工晶状体材料。系统考察了聚合反应时间、温度及引发剂和交联剂的用量等对该水凝胶材料机械强度、平衡水含量(EWC)的影响,并对PHEMA水凝胶的结构和光学性能进行了表征。实验结果表明,PHEMA水凝胶的最佳合成条件为:引发剂0.5wt%,交联剂1.0wt%,反应温度40℃,反应时间36h。在此条件下制备的PHEMA水凝胶的拉伸强度达到0.57MPa,邵氏A硬度为23.0,平衡含水量超过40%,透光率≥97%。     

纤维素透析膜血液相容性的改进在纤维素膜的表面接枝2—甲基丙烯酰乙氧基磷酸胆碱

作为血液透析膜纤维素膜的血液相容性不能令人满意。本文提出将2-甲基丙烯酰乙氧基磷酸胆碱(MPC)接枝到纤维素膜表面,以改善其血液相容性。接枝反应以MPC为单体,铈离子(Ce~(4+))为引发剂,反应混合物经除氧后于40℃反应一小时得产物。体系中微量氧的存在会严重影响反应的进行。产物的X-射线光电子能谱(xps)和付里叶变换红外光谱(FT-IR)证明了MPC接枝到膜表面的事实。反应混合物中〔MPC〕、〔Ce~4〕的改变对接枝反     

聚苯乙烯-孕酮免疫微球的新法制备与检测

本研究采用改进的无乳化剂乳液聚合法制备聚苯乙烯微球,并对聚合反应温度和有机溶剂含量对聚合反应和粒径的影响进行了研究;再将合成的聚苯乙烯微球与孕酮抗体反应,结果表明通过加入少量有机溶剂,提高了聚合反应速度和转化率,制备出了粒径可控的单分散聚苯乙烯免疫微球,粒径在200～800nm之间,微球具有较高的抗体结合容量,且结合后保持了较高的抗体活性.用合成的孕酮免疫胶乳进行免疫凝集实验,观察了反应时间,反应温度的影响,确定了免疫反应的基本反应条件.     

聚苯乙烯—孕酮免疫微球的新法制备与检测

本研究采用改进的无乳化剂乳液聚合法制备聚苯乙烯微球，并对聚合反应温度和有机溶剂含量对聚合反应和粒径的影响进行了研究；再将合成的聚苯乙烯微球与孕酮抗体反应，结果表明通过加入少量有机溶剂，提高了聚合反应速度和转化率，制备出了粒径可控的单分散聚苯乙烯免疫微球，粒径在２００～８００ｎｍ之间，微球具有较高的抗体结合容量，且结合后保持了较高的抗体活性。用合成的孕酮免疫胶乳进行免疫凝集实验，观察了反应时间，反应温度的影响，确定了免疫反应的基本反应条件。     

水溶性O-羟乙基壳聚糖接枝聚乳酸的制备与表征

目的制备用于组织工程的水溶性O-羟乙基壳聚糖／聚乳酸共聚物纤维复合支架。方法首先采用壳聚糖与环氧乙烷反应制备水溶性O-羟乙基壳聚糖,然后以辛酸亚锡为催化剂,水溶性O-羟乙基壳聚糖为引发剂,采用本体封管聚合法,激发D,L-丙交酯开环聚合制备水溶性O-羟乙基壳聚糖-g-聚乳酸共聚物。分别用X射线衍射、红外光谱、扫描电镜和溶解实验对产物的结构与性能进行分析表征。结果改性后的水溶性O-羟乙基壳聚糖能明显提高溶解性能,降低结晶性能和氢键间的相互作用。结论通过改性,为得到水溶性O-羟乙基壳聚糖／聚乳酸共聚物奠定了有利条件,并且此共聚物具有较好的孔隙率和网状结构,这对作为药物支架是一个很好的应用。此外,改性后的共聚物易溶于一些常用的有机溶剂中,有利于以后在组织工程中进一步应用。     

聚乙二醇选择性接枝壳聚糖共聚生物材料

背景：聚乙二醇具有良好的水溶性和生物相容性,兼具亲水性与柔韧性,是改善大分子材料水溶性的常用材料。 目的：把聚乙二醇接枝到壳聚糖的大分子链上,改善壳聚糖的亲水性。 方法：使用铜离子对壳聚糖大分子上的氨基进行保护,将甲氧基聚乙二醇的端羟基与六亚甲基二异氰酸酯缩合成端基为异氰酸酯的聚乙二醇大分子单体,进而与保护后的壳聚糖链节上的羟基进行选择性地缩合接枝共聚反应,合成聚乙二醇接枝壳聚糖共聚物。观察甲氧基聚乙二醇的用量对接枝率、接枝效率及其在水中的溶胀性质的影响。 结果与结论：甲氧基聚乙二醇的用量越多,接枝率越高;当甲氧基聚乙二醇/壳聚糖质量比为5,接枝效率达到最大,为24%;当甲氧基聚乙二醇/壳聚糖质量比为8.75时,平衡溶胀度最高可以达到120%;在水中浸泡同样的时间,甲氧基聚乙二醇的用量越多,聚乙二醇接枝壳聚糖共聚物的溶胀能力越强。     

用聚氧化乙烯改性共聚醚聚氨酯后血小板沉积的研究

为改进商品共聚醚聚氨酯Pellethane 236380A(Pell80A)的血液相容性,作者研究了用不同方法接枝PEO的Pell80A材料,研究了用过氧化二枯基接枝高分子量PEO及甲氧基聚(乙二醇)400丙烯酸脂(MPEGMA-400)的接枝聚合反应.作者还研究了对Pell80A膜和管进行的改性,通过接触角测定来研究改性后膜和管的性能.最后作者研究了Pell80A管内侧用PEO改性对其体外血小板沉积的影响.     

The relationship between leachability of polymerization initiator and degree of conversion of visible light-cured resin

Recently, polymerization-initiator-induced radicals have been identified as a biohazard as well as residual monomers. The present investigation was conducted to clarify the leaching behavior of the polymerization initiator and to measure the relationship between the leached amount of polymerization initiator and the degree of conversion of visible light (VL)-cured resin. Moreover, determining a suitable ratio of polymerization initiator to the base monomer according to the above relationship was carried out. The base monomer (UDMA/TEGDMA) was activated with varying concentrations of polymerization initiator (CQ/DMPT, CQ/DMAEMA) from 0.3-0.9 wt%, respectively, which were exposed to light for 40 s. Gas chromatograph mass spectrometry (GCMS) was carried out to evaluate the leached amount of polymerization initiator. The degree of conversion (DC) of the cured sample was estimated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. As the result, it was recognized that the leachability of the polymerization initiator (CQ, DMPT, and DMAEMA) depended on the degree of conversion of the VL-cured resin. Therefore, the optimal concentration of polymerization initiator can be determined from the relation between the degree of conversion and the leached amount of polymerization initiator, which is about 0.6 wt% for CQ/DMPT (1:1 in weight) and 0.5 wt% for CQ/DMAEMA (1:1 in weight) relative to the UDMA/TEGDMA (1:1 in weight) monomer.     

Modification of poly(propylene) through grafting with dimethyl itaconate in solution

Functionalization of isotactic poly(propylene) (PP) with dimethyl itaconate (DMI) as functional polar monomer using 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101) as radical initiator was carried out in both boiling xylene and decalin as solvent media. The effect of DMI and the initiator concentration on the extent of grafting was studied by varying reaction time and temperature. It was found that temperature affects the percentage of DMI grafted onto PP, which is slightly higher for reactions carried out in xylene than in decalin. The results also show that the amount of DMI incorporated is proportional to the initial DMI and initiator concentrations used in the grafting reaction up to certain concentrations, and thereafter a decrease in the percentage of grafting (G in wt.-%) was found. The maximum value of grafting obtained was 0.7 wt.-%. The melt flow index (MFI) values increase with increasing initial amount of initiator used in the grafting reaction. The degradation of the PP chain is higher when xylene is used as solvent. MFI values of 20–100 were found for modified PP compared with 11.4 for the unmodified polymer.     

Le phényl-1 éthylpotassium,amorceur de polymérisation anionique: Préparation par clivage de l'oxyde de bis(phényl-1 éthyle); étude du milieu réactionnel

1-Phenylethylpotassium ( 5 ), an efficient anionic polymerization initiator in tetrahydrofuran (THF) solution serving as a substitute for 1-methyl-1-phenylethylpotassium in most of its applications, was obtained by cleavage of bis(1-phenylethyl) ether ( 1 ) with potassium. Ether cleavage reactions were carried out in THF at mole ratios potassium/ 1 = 2/1 and 1/1, and the resulting solutions were submitted to careful analysis. All by-products formed in the reaction media were unambiguously identified and their mole fractions in the resulting mixture determined. The presence of these by-products was found not to influence the initiator efficiency.     

Experimental and simulation studies on ethyl acrylate polymerization

An experimental study of the bulk free radical polymerization of ethyl acrylate (EA) initiated by 2,2′-azoisobutyronitrile (AIBN) was conducted. The experiments were carried out based on a factorial design with replicates. The reaction variables investigated were initiator concentration, temperature and chain transfer agent (CTA) concentration (primary octanethiol). The results obtained were used to develop and test a simulation model for EA homopolymerization.     

2-Perbromomethyl-2-oxazoline: a novel trifunctional initiator for the ring-opening polymerization of 2-methyl-2-oxazoline

Polymerization of 2-methyl-2-oxazoline was carried out using a trifunctional initiator, 2-perbromomethyl-2-oxazoline. The degree of polymerization (DP) of the resulting polymer was very close to the feed mole ratio of the monomer to initiator. The number-average molecular weight M?_n increased linearly with conversion, indicating the living nature of the propagating chain end. ¹H NMR and end-group analyses results are consistent with the proposal that the polymer possesses a star-shaped structure.     

Group transfer polymerization of methyl methacrylate catalyzed by potassium bibenzoate/18-crown-6

Group transfer polymerization (GTP) of methyl methacrylate (MMA) was carried out using potassium bibenzoate (KBB) in presence of 18-crown-6 as catalyst and 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene (MTS) as initiator in tetrahydrofuran (THF) at 25°C. The performance of this catalyst was compared with tetrabutylammonium bibenzoate (TBABB) catalyst. Broader polydispersity and lower initiator efficiency were observed for the polymers prepared using KBB/18-C-6 catalyst. Kinetic studies were conducted using both catalysts under identical conditions to better understand the effect of the countercation in GTP.     

Polymerization of vinyl monomers with a benzoic anhydride/dimethylaniline N-oxide system. Vinyl polymerization. 121

The polymerization of methyl methacrylate was carried out in benzene, using benzoic anhydride-dimethylaniline N-oxide system as initiator. It was found that the rate of polymerization was proportional to the square root of the initial concentrations of both benzoic anhydride and dimethylaniline N-oxide, that the polymerization was remarkably accelerated in the presence of alcohols, and that hydroquinone inhibited the polymerization. Polymerizations of acrylonitrile, styrene and vinylidene chloride were also carried out by this system. From the results mentioned here together with the observation on the composition curve of the copolymerization of methyl methacrylate with styrene, it was concluded that the system could initiate radical polymerization of vinyl monomers.     

Synthesis of polymers containing pseudohalide groups by cationic polymerization, 3. Preliminary study of the polymerization and copolymerization of alkenyl monomers containing azide groups

The cationic polymerization or copolymerization of various alkenyl monomers was investigated in the presence of azide groups. The monomers were either of the n-π-donor type, such as vinyl ethers, or π-donors, such as isobutene (2-methylpropene) or styrene. The azide groups were introduced by a suitable comonomer, such as 2-azidoethyl vinyl ether (AEVE) or 4-azidomethyl-styrene (AMS). The initiator was TiCl₄. 3-Azido-2-methyl-1-propene (AMP) (methallyl azide) revealed to be not polymerizable. In the case of vinyl ethers, their cationic polymerization in the presence of azide groups requires high Lewis acid concentrations, according to the work previously carried out on oxetanes. In the case of the less nucleophilic monomers styrene and isobutene it was shown that cationic polymerization takes place provided that the initiator concentration is equal or higher than that of the azide group. This effect was assigned to a complexation between the Lewis acid and the azide group, and consequently the more nucleophilic the monomers (heterocyclics or vinyl ethers) are the lower the required Lewis acid concentration to observe cationic polymerization. Some evidence was found showing that the isobutene polymerization carried out in the presence of a molecular containing an azide group results in an azido-endcapped polyisobutene while in the case of styrene and vinyl ethers cationic copolymerization with comonomers containing azide groups was observed.     

Free Radical Polymerization of Styrene with a New Tetrafunctional Peroxide Initiator

Bulk, free‐radical polymerization of styrene was carried out in the presence of a new tetrafunctional initiator (JWEB50, ATOFINA Chemicals, Inc.). The objective was to investigate the effect of initiator functionality on the free radical polymerization process. Size exclusion chromatography (SEC) with an on‐line multi‐angle laser light scattering (MALLS) detector was used to measure molecular weight (MW), molecular weight distribution (MWD), and radius of gyration (R_g) of polystyrene. These results were compared to those with a monofunctional initiator, LupTBEC, also from ATOFINA. At equivalent molar concentrations, initiation with JWEB50 and LupTBEC produced polystyrene with similar MWs and MWDs. However, the rate of polymerization was faster with JWEB50. When LupTBEC was four times the molar concentration of JWEB50, equal rates of polymerization were achieved for both initiators. The MWDs were again similar, but the MWs were higher for the tetrafunctional initiation. Degree of branching and gelation were also investigated. A mixture of branched and linear polymer was produced by JWEB50, while no insoluble gel was formed.

Decomposition of JWEB50, a tetrafunctional initiator.     

Synthesis and Characterization of Polyacrylamides in Inverse‐Emulsions with an Isoparaffinic Solvent

Inverse‐emulsion polymerizations of aqueous solutions of acrylamide (AM) in an isoparaffinic solvent were carried out using Span 80 as emulsifier. The conversions at the end of inverse‐emulsion polymerizations were investigated by HPLC methods. The conversion has been influenced by the initiator concentration, the monomer concentration and the reaction temperature. The molar masses were determined by viscosity measurements, size exclusion chromatography (SEC) and static light scattering. The influence of initiator concentration, monomer concentration and reaction temperature on the average molar mass of polyacrylamide (PAM) was studied.