Continuity of solvent quality in polymer solutions. Poor-solvent to Θ-solvent continuity in some polystyrene solutions

Critical temperatures for polystyrene/methyl acetate (PS/MA) and polystyrene/ethyl formate (PS/EF) solutions were measured at positive (PS/MA, PS/EF) and negative (PS/MA) pressure. The results confirm that solvent quality is sensitive to pressure; some solvents, designated Θ, at P_nominal ∼ 0, undergo a Θ-to-poor transition at negative pressure, and others, nominally designated “poor,” show a poor-to-Θ transition at positive pressure. Thus, any dichotomous division into sets of “poor” and “Θ” solvents is inaccurate, unless it accounts for the effects of pressure and other variables on solvent quality. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1251–1259, 1997     

Mass spectroscopy and SEC of SRM 1487, a low molecular weight poly(methyl methacrylate) standard

Matrix Assisted Laser Desorption Ionization (MALDI) Time of Flight (TOF) Mass Spectrometry (MS) was used to study the molecular weight distribution (MWD) and the number of α-methyl styrene (α-MeSty) repeat units in SRM 1487, a narrow MWD poly(methyl methacrylate) (PMMA) standard reference material of about 6300 g/mol, which was initiated with α-MeSty. It was found that each PMMA polymer chain had from zero to seven α-MeStys per chain. The MWD of the polymer chains containing a fixed number of α-MeStys was obtained. The MWD, M_w, and the average number of α-MeSty at a given molecular weight from MALDI TOF MS compare well with those obtained from more traditional methods such as ultracentrifugation and Size Exclusion Chromatography (SEC). The implications of the number of α-MeStys per chain is discussed in terms of the chemistry of anionic polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2409–2419, 1997     

Surface modification of coir fibers I: studies on graft copolymerization of methyl methacrylate on to chemically modified coir fibers

Graft copolymerization of methyl methacrylate (MMA) onto chemically modified coir fiber was studied using a CuSO₄–KIO₄ combination as initiator in an aqueous medium in the temperature range of 50–70 °C. Concentrations or [IO₄−] = 0.005 mol/l and [Cu2+] = 0.002 mol/l produce optimum grafting. The effects of time, temperature, amount of coir fiber, some inorganic salts and organic solvents on graft yield have also been investigated. On the basis of experimental findings, a reaction mechanism has been proposed. Evidence of grafting was studied from fourier transform infrared spectroscopy and scanning electron microscopy of chemically modified coir and MMA‐grafted coir. Tensile properties such as maximum stress at break, extension at break and Young's modulus of untreated, defatted, chemically treated and grafted coir fibers were evaluated and compared. Grafted coir fiber showed an increase in tensile properties such as maximum stress at break, extension at break and Young's modulus. Copyright © 1999 John Wiley & Sons, Ltd.     

十八烷基超支化有机物的合成

以十八胺、丙烯酸甲酯为原料,甲醇为溶剂通过迈克尔加成反应制备了0.5G(Generation)超支化有机物,再以0.5G为原料与乙二胺通过酰胺化缩合反应制备了1.0G超支化有机物.并对1.0G进行了合成条件探索,最佳反应条件为n(乙二胺)∶n(0.5G)=60∶1,反应温度60℃,反应时间24 h,产物的产率为99.11%,同时采用红外光谱对两种超支化分子进行了结构表征.     

酯交换法合成丙烯酸氯乙醇酯

丙烯酸卤代烷酯是重要的精细化工原料和中间体,一般的合成方法是直接酯化法。已有文献报道采用酯交换工艺以丙烯酸甲酯为原料制备丙烯酸高碳烷酯和丙烯酸二甲氨基烷酯[1-4]。Nolan等人曾报道了氮杂环卡宾作为催化剂通过酯交换反应合成甲基丙烯酸卤代烷酯[5,6],但是其催化剂制备     

胆酸甲酯羟基酰化反应活性研究

以甲基丙烯酰氯、甲基丙烯酸酐和甲基丙烯酸作酰化剂,研究了胆酸甲酯分子中羟基的反应活性.结果显示,与三种活性不同的酰化试剂作用时,胆酸甲酯分子甾体骨架上三个仲羟基的相对反应活性不同.     

甲基红共振瑞利散射法测定肝素钠

肝素钠（Hep）系葡糖胺聚糖,是蛋白多糖的一种,它具有广泛的生物学功能,是重要的生化药物之一。对不同的疾病,有不同的最适剂量,临床上需进行监控。因此,研究肝素的定量测定方法是非常重要的。肝素的测定最常采用的是生物方法。此外,化学方法有分光光度法、HPLC法,毛细管电泳法,电化学传感器。在国内外利用共振瑞利散射测试肝素钠的也有报道,一般都采用了稀土高价阳离子作增色剂。本文采用的是一种价格便宜的甲基红（methylred）染料作增色剂,结果表明：在近中性的B—R缓冲溶液中,肝素钠与甲基红染料形成离子缔合物后,RRS强度显著增强,并产生了新的RRS光谱;且在一定范围内,RRS强度与肝素钠浓度成正比。在0．060μg/mL～4．00μg/mL范围内呈良好的线形关系,由此对肝素钠注射液进行效价分析,并用此方法测定人体血清中的肝素钠含量,测得人体血清中肝素钠含量为9．18mg／100mL,回收率在90％以上。显然,此法对肝素钠的测定是可靠、灵敏而实用的。     

Synthesis and Crystal Structure of Methyl 12-Bromo- 13,14-furoxan-deisopropyldehydroabietate

1 INTRODUCTION Pine resin is a very abundant renewable natural source mainly composed of diterpenic resin acids with the general formula C19H29COOH, which has been widely applied in industrial manufactures and fine chemicals[1]. Recently, a series of research re- sults show that the resin acid derivatives are poten- tially useful intermediates in the synthesis of drugs active against viruses[2～5]. Their antiviral activity and function as nucleoside analogues or non- nucleoside inhibito…     

The Antioxidant,Cytotoxic and Antimicrobial Potential of Phenolic Acids-Enriched Extract of Elicited Hairy Roots of Salvia bulleyana

Hairy root cultures are valuable sources of a range of phytochemicals. Among them, Salvia bulleyana root culture is a promising source of polyphenols, especially rosmarinic acid (RA), a phenolic acid depside with pleiotropic activity and a wide application in medicine and cosmetology. The aim of the study was to enhance the culture productivity by finding suitable elicitation protocol and to determine its biological potential in terms of antioxidant, anticancer and antimicrobial properties. The total content of phenols and the levels of particular constituents in root extracts were analyzed using HPLC-PDA. Among four elicitors tested (yeast extract; methyl jasmonate, MJA; trans-anethol; and cadmium chloride), MJA was found to be the most effective. The greatest boost in phenolic production (up to 124.4 mg/g dry weight) was observed after three-day treatment with MJA at 100 µM, with an almost 100% improvement compared to the controls (non-treated root culture). The hydromethanolic extract from the elicited culture exhibited strong antioxidant activity with IC₅₀ values of 11.1 µg/mL, 6.5 µg/mL and 69.5 µg/mL for DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid)) and superoxide anion radical, respectively. Moreover, in concentrations of 0.5–5 mg/mL the extract inhibited the growth of LoVo, AGS and HeLa cell lines, but was safe for the L929 cells up to the concentration of 5 mg/mL. The extract also exhibited moderate antimicrobial activity. Thus, the results confirmed that elicitation can be a beneficial strategy for increase the phenolic acid biosynthesis in hairy roots of S. bulleyana, and that such a highly productive culture can show significant biological potential.