Study of cement mortars modified by emulsifier-free latexes

Cationic copolymer latex of vinyl acetate (VA) with methacryloxyethyl trimethylammonium chloride (MTC) and anionic copolymer latex of VA with sodium acrylate (SA) were prepared via emulsifier-free emulsion copolymerization. Modifications of cement mortars by these copolymer latexes were studied, and the results were compared with mortars modified by homopolymer of VA (PVA) as well as with blank mortars. The experimental results showed that flow of the mortars modified by PVA homopolymer and P(VA–MTC) copolymer latexes were increased compared with the blank, whereas a decrease was observed for that modified by P(VA–SA) anionic copolymer latex; a volume expansion was detected in polymer modified mortars by PVA and P(VA–MTC), while no volume expansion was observed in the anionic P(VA–SA) modified mortars; the flexural strength of mortars modified by P(VA–MTC) increased by 79.5% compared to unmodified mortars after 5 day water curing plus 21 day air curing. This value reached 95% when the curing process was followed by a supplementary 24 h vacuum curing. These polymer modified mortars were then subjected to hydration analysis through X-Ray diffraction (XRD). Mechanisms of the mortar modification are discussed based on the characterization results.     

P(nBA-co-St)接枝VC反应中的缓聚及复合物结构与性能

采用丙烯酸正丁酯与苯乙烯共聚物P(nBA-co-St)胶乳为种子,通过乳液接枝共聚氯乙烯(VC)制备了P(nBA-co-St)/PVC复合树脂。粒径分析结果表明,PVC已成功地包覆在种子上,从透射电镜照片能清楚分辨出复合粒子具有核壳结构,文中合理解释了在该接枝共聚过程中显现的缓聚现象。动态力学分析结果表明,随着核层共聚物中PSt组分含量增加,复合材料在低温区的力学损耗峰逐渐移向高温方向,纯PnBA核因比PSt组分更易接枝VC,从而显著影响了复合树脂低温区的玻璃化转变温度。试样冲击断面的扫描电镜分析揭示,P(nBA-co-St)原位增韧PVC的机理源于基体的剪切屈服。     

三氟丙烯本体均聚及与乙烯类单体的溶液共聚合研究

以偶氮双异丁腈(AIBN)作引发剂,研究3,3,3-三氟丙烯(TFP)的本体均聚及其在超临界二氧化碳(sc-CO2)中与烯类单体如醋酸乙烯酯(VAc)、丙烯酸甲酯(MA)、苯乙烯(St)、异丁基乙烯基醚(IBVE)、丙烯酸(AA)5种单体的溶液共聚合反应,测定总单体转化率和TFP转化率随时间的变化及最终产物的平均分子量;对TFP与VAc在sc-CO2中的溶液共聚合除测定上述聚合参数外,采用红外光谱和19F-核磁共振谱表征共聚物的结构,应用核磁共振和电位分析法对比表征共聚物中TFP的结合量、共聚物数均分子量及其分布指数随TFP与VAc的物质的量比、TFP转化率的变化。结果表明:无论是本体聚合还是在sc-CO2中的溶液聚合,TFP都很难发生自由基均聚,但在sc-CO2中TFP却可与上述5种单体发生自由基共聚合,相同条件下50 h TFP的转化率顺序是:Y(TFP-VAc)Y(TFP-IBVE)Y(TFP-MA)≈Y(TFP-St)Y(TFP-AA)。对于TFP-VAc在sc-CO2中的共聚,发现有明显的交替共聚倾向,当n(TFP)∶n(VAc)0.5时,可获得n(TFP):n(VAc)接近1:1的交替共聚物。     

聚氯乙烯接枝聚乳酸的合成及生物降解性

以环己酮为溶剂,将聚氯乙烯(PVC)与聚乳酸(PLA)的钠盐进行反应,合成了以PVC为主链、PLA为支链的接枝聚合物(PVC-g-PLA)。讨论了实验条件对产物接枝率的影响,用核磁共振氢谱(1H-NM R)、红外光谱(FT-IR)和凝胶渗透色谱(GPC)对接枝聚合物进行了表征。采用土壤掩埋试验和扫描电镜(SEM)分析的方法,研究了接枝物的生物降解性。     

MMA/MPEOMA/VSA copolymer as a novel blood-compatible material: ex vivo platelet adhesion study

MMA/MPEOMA/VSA copolymers with both pendant polyethylene oxide (PEO) side chains and negatively chargeable side groups were synthesized by random copolymerization of methyl methacrylate (MMA), methoxy PEO monomethacrylate (MPEOMA; PEO mol. wt, 1000), and vinyl sulfonic acid sodium salt (VSA) monomers with different monomer composition to evaluate their blood compatibility. MMA/MPEOMA copolymer (with PEO side chains) and MMA/VSA copolymer (with negatively chargeable side groups) were also synthesized for the comparison purpose. The synthesized copolymers were coated onto polyurethane (PU) tubes (inner diameter, 4.6 mm) by a spin coating. The platelet adhesion of the MMA/MPEOMA/VSA copolymer-coated tube surfaces was compared with that of tube surface coated with MMA/MPEOMA or MMA/VSA copolymer with similar MPEOMA or VSA composition, using an ex vivo canine arterio-artery shunt method. The platelet adhesion was evaluated by radioactivity counting of technetium (99mTc)-labeled platelets adhered on the surfaces after 30 and 120 min of blood circulation. The MMA/MPEOMA/VSA copolymer (monomer molar ratio 9/0.5/0.5 or 8/1/1) was better in preventing platelet adhesion on the surface than the MMA/MPEOMA or MMA/VSA copolymer with similar MPEOMA or VSA composition, probably owing to the combined effects of highly mobile, hydrophilic PEO side chains and negatively charged VSA side groups.     

Synthesis and electrochemical probing of water-soluble poly(sodium 4-styrenesulfonate-co-acrylic acid)-grafted multiwalled carbon nanotubes

Water-soluble poly(sodium 4-styrenesulfonate-co-acrylic acid)-grafted multiwalled carbon nanotubes (MWNT-g-P(SSS-co-AA)) with core-shell nanostructure were successfully synthesized by in situ free radical copolymerization of sodium 4-strenesulfonate (SSS) and acrylic acid (AA) in the presence of MWNTs terminated with vinyl groups; their structure was characterized by FTIR, (1)H NMR, Raman, TGA and TEM. The results showed that the thickness and content of the copolymer layer grafted onto the MWNT surface are about 7-12?nm and 82.3%, respectively. The P(SSS-co-AA) covalently grafted on MWNTs provides MWNT-g-P(SSS-co-AA) with good hydrophilicity and solubility in water. Then a novel MWNT-g-P(SSS-co-AA)-modified glassy carbon electrode was fabricated by coating; its electrochemical properties were evaluated by electrochemical probe of K(3)[Fe(CN)(6)], and its catalytic behaviors to the electrochemical oxidation processes of dopamine (DA) and serotonin (5-HT) were investigated. Since the MWNT-g-P(SSS-co-AA)-modified electrode possesses strong electron transfer capability, high electrochemical activity and catalytic ability, it can be used in sensitive, selective, rapid and simultaneous monitoring of biomolecules.     

The effect of matrix polarity on the properties of poly(o-methoxyaniline)–EVA blends

Poly(o-methoxyaniline) (POMA) doped with p-toluene sulfonic acid (TSA) was successfully melt blended with ethylene vinyl acetate copolymer (EVA). The effect of the matrix polarity as well as the blend composition on the properties of the blends was investigated using two grades of EVA as matrix. The lower polarity EVA contains 8% vinyl acetate (VA) (EVA₈) and the higher polarity EVA contains 33% VA (EVA₃₃). The surface resistivity of the POMA-EVA blends was found to decrease with an increase of POMA loading. The POMA-EVA₈ blends had a lower surface resistivity than POMA-EVA₃₃ blends which is attributed to the presence of a higher proportion of conductive POMA particles in the surface region resulting from the larger polarity difference between the POMA and the EVA₈ matrix. More uniform dispersion is observed from scanning electron microscopy (energy-dispersive X-ray spectroscopy) for POMA in EVA₃₃ compared to POMA in EVA₈ and this has been interpreted as being a consequence of the similar polarities between POMA and EVA₃₃. The mechanical properties of the blends were found to be affected by both POMA loading and matrix polarity. The oxygen barrier property of the POMA-EVA blends was found to increase with POMA loading in both high and low polarity EVA matrices.     

Comparative Evaluation of Direct Compression Ampicillin Formulations

Direct compression formulations were developed for ampicillin using methyl vinyl ether/maleic anhydride copolymer (I) and vinyl acetate/crotonic acid copolymer (II) as binders. A comparison was made between these formulations and wet granulation method using gelatin as binder regarding the chemical stability of ampicillin as a function of relative humidity (55 to 90%) and temperature (40 to 75°C). Polymer I showed least moisture uptake followed by polymer II and gelatin. The mechanism suggested here involves moisture uptake and dissolution followed by chemical decomposition. The temperature had lesser effect on stability because of low activation energies but an Arrhenius relationship was established for three formulations studied. It was concluded that formulation using polymer I gives the most ideal combination of physiochemical properties for the direct compression of ampicillin in solid dosage forms.     

稳定自由基存在下嵌段共聚物的合成及表征

合成了一系列不同分子量，分子链末端带有稳定自由基（2，2，6，6－四甲基－1－哌啶氧化物，TEMPO）的聚苯乙烯大分子引发剂，分别引发甲基丙烯酸丁酯（BMA），甲基丙烯酸乙酯（EMA），甲基丙烯酸甲酯（MMA），甲基丙烯酸辛酯（OMA），醋酸乙烯酯（VAc)，二甲基丙烯酰胺（DMA），丙烯酸二甲胺基乙酯（DAEA）等7种极性单体形成两嵌段共聚物，聚苯乙烯－聚甲基丙烯酸酯嵌段共聚物的分子量可控，分子量分布较窄，单体转化率较高，醋酸乙烯酯和丙烯酸二甲胺基乙酯在相同条件下的嵌段共聚难以达到高转化率，嵌段共聚物经GPC和1H0NMR表征。     

N-异丙基丙烯酰胺共聚物的温敏性

采用自由基水溶液聚合方法制备出了N-异丙基丙烯酰胺(N IPA)温敏共聚物P(AM-N IPA);首次在P(AM-N IPA)结构中引入丙烯酸钠(N aAA)单体结构单元,合成了离子型共聚物P(AM-N IPA-N aAA);考察了共聚物P(AM-N IPA)和P(AM-N IPA-N aAA)溶液温敏性的影响因素;分别采用荧光光谱分析法以及乌氏黏度计稀释法对共聚物溶液温敏机理进行了研究。结果表明,不同共聚单体的配比以及单体含量对共聚物溶液低临界溶解温度(LCST)均有显著影响;当温度高于共聚物低临界溶解温度时,共聚物分子链上的疏水基团的缔合作用增强,导致疏水聚集结构的形成,聚合物分子链发生去溶剂化作用,在共聚物稀溶液中表现为线团收缩,在共聚物亚浓溶液中表现为共聚物分子间聚集发生相分离。     

超临界二氧化碳中CTFE和VAc共聚物的合成及性能

以超临界二氧化碳流体为反应介质,制备了醋酸乙烯酯(VAc)和三氟氯乙烯(CTFE)的共聚物。研究了单体配比、引发剂用量、压力及温度对反应的影响,并对产物的结构及膜性能等进行了表征。实验结果表明,通过控制反应条件可以得到不同分子量、不同氟含量的共聚物,且共聚物中氟含量的不同是聚合物膜对溶剂接触角变化的原因。     

氧化降解程度对接枝共聚改性淀粉性能的影响

以玉米淀粉为原料,(NH4)2S2O8为氧化剂,采用一步氧化法对淀粉氧化降解,进而与乙烯基类单体接枝共聚,制备了乙烯基类单体接枝共聚改性淀粉,并应用于蓝湿革复鞣工艺。结果表明,当(NH4)2S2O8用量为7.5%、降解温度为95℃、降解时间为30min时,共聚物的接枝率、接枝效率和单体转化率较高,且共聚物对坯革具有一定的复鞣填充和捕获游离甲醛的作用。FT-IR、XRD和TGA结果表明乙烯基类单体已成功接枝于氧化降解淀粉分子上。     

玻璃纤维/环氧乙烯基酯树脂复合材料的层间增韧及其低温下低速冲击性能

采用真空辅助成型工艺(VARI)制备了四种无纺布(聚酰胺(PA)、聚氨酯弹性体橡胶(TPU)、乙烯-醋酸乙烯共聚物(EVA)、共聚酯(PEs))层间改性的玻璃纤维/环氧乙烯基酯树脂(GF/EVER)复合材料层合板.在温度为20℃下进行落锤冲击实验,对比分析了不同层间改性的GF/EVER复合材料层合板的低速冲击响应特性和...     

New amphoteric flocculant containing beta-cyclodextrin,synthesis, charaterization and decolorization properties

To react with the cationic monomer, N-trimethylaminoethylmethacrylate chloride (TMAEMC), a β-CD derivative carrying vinyl carboxylic acid groups (β-CD-MAH) was designed and synthesized via esterfying reaction between β-CD and maleic anhydride (MAH). Whereafter, a water-soluble amphoteric flocculant, the copolymer of TMAEMC and β-CD-MAH (β-CD-MAH-TMAEMC) has been synthesized by means of free radical copolymerization using the ammonium persulfate (APS) and sodium bisulfite (SBS) redox system as the initiator. The copolymer structure was demonstrated by FT-IR, ¹H NMR, SEM characterizations. Its excellent flocculated decolorization properties were evaluated with Acid Light Yellow 2G solutions using a jar test method. With the mass ratio of 1/10 (w/w) between the flocculant and dye, and at pH 4 and 20 °C of the initial dye solution, the maximum color removal reached. The charge neutralization played a dominant role during the flocculated decolorization process, although the inclusion of dye molecules into the cavities of β-CD well maintained in side chain of β-CD-MAH-TMAEMC also contributed to the conglomerates and floccules.     

Nanostructuration of self-assembled poly(styrene-b-isoprene-b-styrene) block copolymer thin films in a highly oriented pyrolytic graphite substrate

Highly oriented pyrolitic graphite (HOPG) is a useful substrate to visualize epitaxial formation due to its crystallographic structure. The morphology of a poly(styrene-b-isoprene-b-styrene) block copolymer thin film on a HOPG substrate was investigated by atomic force microscopy. Block copolymer domains generated a morphology with triangular regularity. This arrangement was induced by the HOPG substrate structure due to van der Waals attraction between the HOPG π-conjugated system and aromatic ring of polystyrene domains. However, increasing the film thickness, the substrate effect on the surface morphology decreased. As a consequence, film surfaces showed the coexistence of different structures such as highly aligned cylinders and perforated lamellae. When film thickness exceeded a threshold value, the substrate did not have effect in the surface arrangements and the surface showed a similar morphology to that existing in bulk.     

Determination of the compositional distribution of copolymers by frontal analysis continuous capillary electrophoresis

Frontal analysis continuous capillary electrophoresis (FACCE) was carried out for a series of random copolymers of an ionic monomer, sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS), and a nonionic monomer, acrylamide (AAM). The electropherograms appeared in order of anionic content and were generally sigmoidal, in contrast to that of hyaluronic acid (HA), which was abrupt and discontinuous. This difference could be related to the compositional heterogeneity of the copolymers, completely absent in the biopolymer. Through the range of copolymer composition (10-100% AMPS) the relationship between average mobility and nominal AMPS content could be described by a calibration curve, making it possible to deduce the compositional distribution of copolymer samples.     

氢氧化钠催化淀粉/乳酸接枝共聚物的合成

以氢氧化钠(NaOH)为催化剂,采用原位一步法合成了淀粉/乳酸接枝共聚物。用红外光谱(IR)、扫描电镜(SEM)和核磁共振(1H-NMR)测试方法对淀粉/乳酸接枝共聚物的结构进行了表征。IR和1H-NMR核磁图谱均表明,聚乳酸确实接枝到了淀粉上;SEM分析表明,经乳酸接枝改性后的淀粉的形貌发生了很大变化。同时通过改变NaOH溶液浓度,原料比例,聚合温度和聚合时间考察了反应条件对淀粉与乳酸接枝率的影响,结果表明,当NaOH溶液浓度为0.4 mol/L,淀粉∶乳酸(质量比)为1∶6,聚合温度为90℃,聚合时间为9 h时,淀粉的接枝率可达33.6%。     

丙烯酸、丙烯醇、乙烯基咪唑三元共聚物的合成

通过沉淀聚合的方法,采用偶氮二异丁基腈为引发剂,将乙烯基咪唑、丙烯酸、丙烯醇三元共聚,制备了一种具有类似于纤溶酶生物活性的新型高分子。探讨了合成条件对聚合过程、黏度及分子量的影响,并对利用红外光谱(IR)和核磁共振(NMR)对该共聚物进行了结构表征。纤维蛋白平板实验证实该共聚物能溶解血栓。     

The effect of flame-retardants on the properties of acrylic and modacrylic fibres

In this study, flame-retardant additives such as tributyl phosphate, tri(dibromopropyl) phosphate, aluminium hydroxide powder and aluminium hydroxide gel are used for acrylic fibre (acrylonitrile and vinyl acetate copolymer), and calcium phosphate and antimony oxide are introduced into modacrylic fibre (acrylonitrile and vinylidene chloride copolymer). Investigations are carried out on the effect of these flame-retardants on the thermal properties, mechanical properties, morphology and flammability of acrylic and modacrylic fibres. The results show that the effect of additives on the rate of coagulation during spinning can be understood from the changee of morphology of the fibres. Tri(dibromopropyl) phosphate and antimony oxide are good flame-retardant and good synergistic flame retardant, respectively.     

Compositional and structural studies of vinylidene chloride/vinyl chloride copolymers by pyrolysis gas chromatography

A pyrolysis gas chromatography approach has been developed to study the composition and structure of vinylidene chloride/vinyl chloride copolymers. The composition and number average sequence length, which reflects the monomer arrangement in the polymer, were calculated using formulas that incorporate the pure trimer peak intensities and hybrid trimer peak intensities. Because of the reactivity difference between vinyl chloride and vinylidene chloride monomers, the structure of the polymer has been further investigated on the basis of the percentage of grouped monomers (i.e., the number average sequence length for vinyl chloride and vinylidene chloride repeat units). For the vinylidene chloride/vinyl chloride copolymer examined in this study, the composition and number average sequence length elucidated from the pyrolysis gas chromatography study are compared to the product composition specification and/or the composition measured by (1)H-NMR.