Study on Synthesis and Chain Extension of Poly(Lactic Acid-co-Glycolic Acid)

聚乳酸－乙醇酸(PLGA)是一类重要的生物可降解材料。通过改变组成、分子量等可以调节PLGA的生物相容性、生物降解速度、材料的强度和模量，因此，PLGA在生物医学工程领域有广泛的应用。 目前，工业上主要采用开环聚合法制备PLGA，但因合成路线复杂导致产品价格昂贵。降低产品价格最有效的途径之一是采用简单易行的熔融缩聚法合成PLGA。本文在不添加催化剂的条件下，由乳酸（LA）、乙醇酸（GA）直接熔融缩聚合成无毒的PLGA，并探讨聚合温度（Tp）、反应时间、单体投料比等对分子量的影响，结果表明：Tp越高，PLGA的重均分子量所能达到的最大值越小；欲获得高分子量的PLGA，最佳的Tp范围为160～1...Poly(lactic acid-co-glycolic acid) (PLGA) is one of the most important biodegradable polyester materials whose biocompatibility,degradation rate,strength and modulus can be tailored to different needs in biomedicine engineering field by adjusting monomer ratio and molecular weight. Nowadays, PLGA is mostly prepared by ring-opening polymerization, but the resulting product is too expensive due t...学位：理学硕士院系专业：材料学院材料科学与工程系_高分子化学与物理学号：2072007115002

锆促进纳米氧化镍催化剂的制备及其对乙烷氧化脱氢制乙烯的催化性能

用尿素均匀沉淀法制备了不同含量锆促进的纳米氧化镍催化剂 ,并考察了其对乙烷氧化脱氢制乙烯的催化性能 .结果表明 ,纯纳米氧化镍在优化条件下的最高乙烯收率为 2 1 7% ;而锆促进的纳米氧化镍催化剂对乙烯选择性和高温抗乙烷裂解性能都有明显改善 .15 %ZrO2 NiO表现出最佳的催化性能 ,在 4 10℃下 ,乙烷转化率为 6 1 5 % ,乙烯选择性为 6 8 6 % ,乙烯收率为 4 2 2 % ;该催化剂在 4 2 0℃经 36h反应 ,乙烯收率仅下降约 4 % ,粒子没有发生明显的团聚 ,表现出较好的稳定性 .XRD结果表明 ,锆促进的纳米氧化镍粒子较纯纳米氧化镍粒子小 ,平均粒径为 5～ 7nm ;助剂锆以无定形的ZrO2 形式存在 .O2 TPD MS结果表明 ,锆的加入提高了催化剂中较高温度下脱附的氧物种量 ,降低了较低温度下脱附的氧物种量 .H2 TPR结果显示 ,锆促进的纳米氧化镍催化剂较纯纳米氧化镍难以完全还原

锆促进纳米氧化镍催化剂的制备及其对乙烷氧化脱氢制乙烯的催化性能

用尿素均匀沉淀法制备了不同含量锆促进的纳米氧化镍催化剂 ,并考察了其对乙烷氧化脱氢制乙烯的催化性能 .结果表明 ,纯纳米氧化镍在优化条件下的最高乙烯收率为 2 1 7% ;而锆促进的纳米氧化镍催化剂对乙烯选择性和高温抗乙烷裂解性能都有明显改善 .15 %ZrO2 NiO表现出最佳的催化性能 ,在 4 10℃下 ,乙烷转化率为 6 1 5 % ,乙烯选择性为 6 8 6 % ,乙烯收率为 4 2 2 % ;该催化剂在 4 2 0℃经 36h反应 ,乙烯收率仅下降约 4 % ,粒子没有发生明显的团聚 ,表现出较好的稳定性 .XRD结果表明 ,锆促进的纳米氧化镍粒子较纯纳米氧化镍粒子小 ,平均粒径为 5～ 7nm ;助剂锆以无定形的ZrO2 形式存在 .O2 TPD MS结果表明 ,锆的加入提高了催化剂中较高温度下脱附的氧物种量 ,降低了较低温度下脱附的氧物种量 .H2 TPR结果显示 ,锆促进的纳米氧化镍催化剂较纯纳米氧化镍难以完全还原

乙烷在纳米氧化镍上温和氧化脱氢制乙烯

用溶胶 -凝胶法制备的纳米氧化镍具有较好的乙烷氧化脱氢低温反应活性 .3 80℃下焙烧的NiO粒子大小在 8nm左右 ,与大尺寸氧化镍相比 ,获得相同收率时反应温度大约下降 12 5℃ .并通过BET ,TPR ,TPD ,XPS等手段对不同焙烧温度的氧化镍催化剂进行表征 ,研究其粒子大小与对氧的活化能力及反应活性的关联

Synthesis and Characterization of Epoxidized Styrene-butadiene-styrene Triblock Copolymer

以H2O2为氧化剂,利用原位反应生成的磷钨杂多酸铵盐为催化剂在水/有机溶剂两相体系中使SbS环氧化,研究了反应条件对环氧化反应的影响,并用1H-nMr、fT-Ir、gPC对环氧化SbS(ESbS)的结构进行表征.研究结果表明该环氧化方法具有反应条件温和、反应速度快、新生成的环氧基不发生开环水解反应等优点;但反应中伴随有SbS交联和降解副反应,严重影响ESbS性能.通过添加0.3%--0.6%抗氧剂、选择甲苯/三苯基磷酸酯混合溶剂为有机相可以抑制交联和降解副反应,提高反应选择性,使制得的ESbS具有良好的性能.SBS epoxidation reaction was preformed in water/solvent biphasic system in the presence of in-situ prepared methyltrioctylammoniumtetrakis(diperoxotungstate)phosphate,using H2O2 as oxidant.The effect of reaction conditions on epoxidized SBS properties was investigated.The epoxidized SBS structures and molecular weight distribution were also characterized by 1H-NMR,FT-IR and GPC.It was demonstrated that epoxidation method used in this paper had many advantages,such as mild reaction condition,fast epoxidation speed,free of epoxy group hydrolysis reaction.But serious crosslinking reaction also occurred during epoxidation reaction,which could result in reduced solubility of epoxidized SBS.In order to improve selectivity of epoxidation reaction,0.3%--0.6%(by mass) antioxidant was used,toluene/triphenyl phosphate mixture was chosen as organic phase solvent.Under these reaction conditions,high epoxy degree and well solubility of epoxidized SBS can be gained

Synthesis of Poly(Lactic Acid-co-Glycolic Acid) by Direct Melt Polycondensation Without Catalysts

以乳酸(lA)、乙醇酸(gA)为原料,在无催化剂、高真空条件下直接熔融缩聚合成聚乳酸-乙醇酸(PlgA)无规共聚物,对产物进行了gPC、fTIr1、H-nMr表征,并研究了反应时间、聚合温度、lA/gA投料比对PlgA分子质量的影响.结果表明:在所研究的聚合温度范围内,PlgA分子质量随聚合时间的延长先增大后减小;聚合温度越高,PlgA所能达到的最高分子质量越小,最佳聚合温度范围为160--170℃,最佳反应时间范围为57--69 H;在相同反应条件下,lA/gA投料比越小,PlgA分子质量越大.该研究为PlgA的合成提供一种安全、经济、有效的新途径.Poly(lactic acid-co-glycolic acid)(PLGA) was synthesized with lactic acid and glycolic acid by direct melt polycondensation without catalysts.The products were characterized by GPC,FTIR,1H-NMR.In this work,the effects of reaction time,polymerization temperature(Tp) and LA/GA feed ratio on molecular weight were investigated.Results indicated that in the range of Tp we discussed,molecular weight gradually increased and then decreased as the reaction time increased;the maximal molecular weight of PLGA decreased while Tp increased;the optimal ranges of Tp and reaction time were 160--170 ℃ and 57--69 h respectively;under the same reaction conditions,the molecular weight of PLGA increased while the LA/GA feed ratio decreased.The objective of this study is to develop an economical,safe and effective method for the synthesis of PLGA

硅光电负阻器件的光双稳态瞬态特性

在该文中，一方面对电路参数与硅光电负阻器件的光学双稳态开关时间的关系进行了研究，另一方面对器件在低、中、高三个不同输入光强区的光学双稳态响应的变化趋势进行了研究。硅光电负阻器件包括有各种类型，该文主要对“λ”型双极光电负阻晶体管(PLBT)以电阻和光电二极管作为负载的情况进行了讨论

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel