核中含有羧基官能团的聚合物胶束的高效制备

通过化学交联反应诱导胶束化以较高的效率制备了PMCC(聚合物的质量浓度高达50 g/L). 首先制备嵌段共聚物聚苯乙烯-b-聚丙烯酸(PS-b-PAA), 然后对PAA嵌段中的羧基实行酰氯化, 在酰氯化产物聚苯乙烯-b-聚丙烯酰氯(PS-b-PACl)的共同溶剂二氯甲烷中加入交联剂乙二醇交联PACl嵌段. 交联反应使得PACl嵌段聚集, 同时, PS嵌段的保护作用使得PACl嵌段的聚集在有限个分子链间发生, 从而生成以PS为壳, 以含有羧基官能团的聚丙烯酸酯交联网络为核的PMCC.     

八氟环丁烷等离子体聚合物结构的ESCA和IR表征

采用外部电极电容耦合的等离子体聚合装置,以Ar、N_2H_2和Hc为等离子气体,在不同功率、压力、等离子气体及等离子气体对单体比率的反应条件下,在辉光放电中进行八氟环丁烷聚合。用电子能谱(ESCA)和红外光谱(IR)法对聚合物结构进行表征。发现聚合物中存在C、F、Si、O、N和H等六种元素,并对可能存在的基团进行探讨。通过对ESCA(C_18 谱的分析,研究了聚合物支化与交联程度对反应条件的依赖关系,及其和聚合与刻蚀竞争历程之间存在的内在联系。     

Backward/Hopf bifurcations in SIS models with delayed nonlinear incidence rates

The classical SIS model with a constant transmission rate exhibits simple dynamic behaviors fully determined by the basic reproduction number. Behavioral changes and intervention measures influenced by the level of infection, likely with a time lag, require the transmission rate to be a nonlinear function of the total infectives. This nonlinear transmission, as shown in this paper via a combination of qualitative and numerical analysis, can generate interesting dynamical behaviors at the population level including backward and Hopf bifurcations. We conclude that sustained infections and periodic outbreaks can be consequences of delayed changes in behaviors or human intervention.      

Biodegradable packing materials based on waste collagen hydrolysate cured with dialdehyde starch

Hydrogels of collagen hydrolysate (H) of mean M _w 15–30 kDa obtained from waste collagen from meat casings manufacture, cross-linked with 15% (based on H) polymeric dialdehyde starch (DAS), have a marked tendency to ageing, which shows in hydrogel gradually increasing rigidity and decreasing thermo-reversibility. Methods of thermal analysis (DSC, TG) proved that ageing of hydrogels is not related with a non-equilibrium state of the cross-linking reaction but is rather given by increasing density of inter-chain hydrogen bonds between polypeptide segments of H. Plasticizing effect of DAS on H is not too pronounced but the difference between glass transition temperature of dry xerogel T _g = 189.5±2.5°C and temperature of starting degradation (DAS component) 241.4±12.7°C offers certain space for processing these xerogels into biodegradable (edible) packaging material by usual plastics technologies. Films obtained from the reaction mixture by casting and drying at room temperature after thermal processing (105°C for 4 h) dissolve at room temperature only after 350 h. This effect can be employed for time-controlled releasing of active substances from such biodegradable (edible) packages.     

Laws of the single logarithm for delayed sums of random fields II

In an earlier paper we extended Lai's (1974) law of the single logarithm for delayed sums to a class of delayed sums of random fields. In this paper we allow for more general windows.     

可控交联聚醚醚酮动态流变学行为的研究

聚芳醚酮类材料因其优异的综合性能在许多领域得到广泛应用 [1,2 ] .许多研究者通过提高聚芳醚酮分子链的刚性度来实现进一步提高其使用温度 ,但由于其在高温时流动性下降 ,熔体粘度增大 ,给加工及应用带来很大困难[3] .基于此 ,我们将可在高温或辐照条件下发生交联反应的硫醚结构作为交联点引入到聚醚醚酮主链中 ,合成了可控交联的聚醚醚酮[4 ,5] .聚合物的分子结构及其熔体中分子的内部作用可以用流变学进行研究 .因此 ,我们用动态流变学实验监测跟踪聚合物的交联反应过程 ,研究可控交联聚醚醚酮的交联反应动力学 ,为设计改造分子结构以满…     

Curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide or copper(II) oxide

This paper discusses the curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide (Cu₂O) or copper(II) oxide (CuO). The results revealed that the cross-linking degree of CR/BR blends decreased with the increasing amount of butadiene rubber (BR) in the blends. The mechanical properties of cured CR/BR blends depended on the proportion of elastomers in blends, as well as on the type and amount of the cross-linking agent (Cu₂O, CuO). The cross-linking of CR/BR/Cu₂O or CR/BR/CuO blends followed according to cationic mechanism, using Lewis acid, copper(I) chloride (CuCl) or copper(II) chloride (CuCl₂) generated in situ. Additionally, the prepared compositions, both unfilled and filled, were characterized by very high resistance to flame.     

PLG-g-TA/RGD酶催化交联水凝胶用于透明软骨细胞黏附和三维细胞培养

制备了一种基于聚谷氨酸-g-酪胺/cRGDfk(PLG-g-TA/RGD)的新型酶催化交联水凝胶, 用于兔透明软骨细胞黏附和三维细胞的培养. PLG-g-TA/RGD聚合物材料在辣根过氧化物酶(HRP)和过氧化氢(H₂O₂)存在下, 能够通过酪氨基团的自交联快速形成水凝胶. 环状多肽(cRGDfk)的引入能够显著提高材料的溶液-凝胶转变速率和凝胶强度. 透明软骨细胞在水凝胶表面黏附3 d后, 在PLG-g-TA/RGD水凝胶表面有更多的细胞黏附; 将透明软骨细胞包裹在水凝胶内培养1, 4, 7 d后, 细胞在PLG-g-TA/RGD水凝胶内增殖效率明显高于对照组PLG-g-TA水凝胶. 细胞实验结果表明, 该水凝胶材料具有良好的生物相容性. cRGDfk的引入, 促进了透明软骨细胞的黏附和增殖, 显示了PLG-g-TA/RGD水凝胶材料在三维细胞培养方面的应用潜力.     

聚苯乙烯光子晶体薄膜的光化学行为

研究了紫外光照下聚苯乙烯（PS）光子晶体薄膜的表面形貌、光学性质及浸润性变化. 傅立叶红外光谱对紫外光照前后薄膜表面的化学成分进行了表征,结果表明紫外光照后PS微球表面产生亲水性极性基团羰基. 扫描电子显微镜照片表明随着紫外光照时间的延长,PS微球发生收缩、变形甚至熔化. 原位反射和透射光谱表明在光照20 min内,光子晶体薄膜能够保持良好的光学性能,且薄膜由疏水表面转变为亲水表面. 因此,控制光照时间可以制备得到具有良好光学性能的亲水性聚合物光子晶体薄膜,对于光子晶体在特殊环境下的应用具有重要的意义.     

左旋多巴-壳聚糖微球的制备及其释药性能

采用乳化分散-离子交联法,以三聚磷酸钠为离子交联剂,制备了左旋多巴-壳聚糖微球,并考察其理化性质和药物释放性能。偏光显微镜观察表明,得到的微粒基本成球;经激光粒度仪测定,其平均粒径约为3.5μm。红外光谱分析表明,壳聚糖中的氨基质子化后与三聚磷酸钠以静电结合,而左旋多巴则被包裹在壳聚糖微球内。DSC及XRD分析结果表明,微球内部存在左旋多巴结晶,而壳聚糖则以无定形聚集态存在。TG分析结果表明,壳聚糖与三聚磷酸钠结合后分解温度降低。微球的药物释放性能显pH依赖性,在酸性环境下,微球的释药速率随壳聚糖浓度的增加而降低,随载药比例的增大而降低;而在碱性介质中总体的释药速率要比酸性介质中的大。