【作者】 宣理静；

【导师】 钱锦文；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2006， 硕士

【摘要】 聚电解质层层自组装技术(Layer-by-layer)由于操作简便、可用于制备超薄膜的物质的种类和数量很多、膜厚度和结构纳米范围内调控,其在药物缓释放,生物传感器,光电材料和分离膜等领城具有广泛的应用。本文以聚二烯丙基二甲基氯化铵(PDDA)和聚苯乙烯磺酸钠(PSS)为材料,从聚电解质稀溶液性质研究出发系统考察聚电解质自组装过程中影响吸附量和膜结构的主要因素。在国内,将聚电解质自组装膜作为渗透汽化膜分离的研究更未见报道,具有重要的研究意义。 本文首先采用紫外光谱法(UV-VIS)研究了PDDA/PSS静电自装过程中的非静电力问题,在处理过带负电的石英片上能吸附带同种电荷的PSS,组装量随石英片表面粗糙度增加、PSS浓度升高以及温度的下降而增加。表明聚电解质静电自组装过程中在适当条件下明显存在非静电力驱动下的自组装行为。 其次,采用紫外光谱法、接触角仪、粘度法研究了PDDA/PSS自组装的机理和影响吸附量和膜结构的主要因素。紫外结果发现随着聚电解质的浓度、溶液的盐浓度、溶液的酸碱度(pH)、混合溶剂(乙醇/水)中有机溶剂的含量和组装温度的变化,PDDA/PSS自组装膜的吸附量呈现出不变、增加和减小的现象。PDDA,PSS聚电解质溶液在相对应的组装条件下的特性粘数与自组装膜的紫外吸光度(吸附量)呈反比关系。聚电解质在溶液中线团较收缩,静电自组装膜的吸附量越大。用接触角法研究了PDDA/PSS膜的表面润湿性,多层膜表面接触角随着层数开始呈不规则变化后呈现锯齿状变化规律,表明了PDDA/PSS自组装膜的结构分为2个区:Ⅰ区有缺陷的“前驱层”和Ⅱ区规则的交替沉积的“本体层”。 最后,在聚酰胺(PA)反渗透底膜上成功的制备出PDDA和PSS聚电解质自组装膜,作为渗透汽化膜分离异丙醇(95%)/水(5%)混合体系。在含盐组装溶液中,其渗透汽化性能随组装层数(N)的增加,分离因子(α)增大和渗透通量(J)下降,一般N小于10的膜就可获得较好的渗透汽分离化性能。当层数为6.5个双层,盐浓度为0.75mol/L和料液温度为55℃时,分离因子和通量各达极大值和极小值,247和1498g/m~2h。随着操作温度的提高,分离因子α和通量J呈同步增大的变化规律。更多还原

【Abstract】 Recent years, the so-called layer-by-layer (LBL) deposition technique of oppositely charged polyelectrolytes can be successfully applied to prepare organic ultrathin films. For their simple fabrication (operation), precisely controlled film thickness and structure, broad range of materials that is available for incorporation into polyelectrolyte multilayers (PEMs), they are applied abroad in many different fields such as drug release, biosensors, photoelectric materials and membrane separation. This paper is concerned with the viscosity behaviour of dilute aqueous solutions of polyelectrolytes (PDDA& PSS) and is a system investigation of the main factor that influenced the buildup of PEMs and its structure. It is valuable to study PEMs as the pervaporation membrane for dehydration of isopropanol.Firstly, the influence of non-eletrostatic force during the alternating electrostatic layer-by-layer (LBL) adsorption of oppositely charged PDDA and PSS was investigated by UV-VIS spectrum. PSS can be adsorbed on clean silica with the same sign charge, the adsorption mass was increased with the increasing roughness of silica surface, PSS concentration, and with decreasing adsorption temperature. These indicated that the driving force of oppositely charged PDDA/PSS isn’t only electo-static force, non-coulomb force also play an important role during the buildup of PEMs.Secondly, the adsorption mechanism and main factor that influenced the buildup of PEMs and its structure were studied using UV-VIS spectrum, Contact angle measurement (CA) and viscometry. It was found that the adsorption amount can be constant, increase and decrease as the concentration of polyelectrolyte, salinity, pH, composition of the organic solvent/water mixtures and adsorption temperature varies. The viscosity study of PDDA and PSS at corresponding adsorption conditions indicated that there being a inverse proportion relationship between intrinsic viscosity of the polymer and the adsorption amount. The smaller the coil size contracted, the more mass the polymer adsorbed. PEMs’ surface contact angle as a function of layer number showed a serrate state variation. The wetting property of PDDA/PSS PEMsby Contact angle measurement demonstrated that polyelectrolyte multilayers composed of two distinct zones. Zone I is premonitory layer comprised of one or a few polyelectrolyte layers close to the substrate. Zone II is the "bulk" film comprised of regularly alternating deposition of two oppositely charged polyelectrolytes.At last, PDDA/PSS PEMs was successfully prepared on polyamide (PA) reverse osmosis substrate membrane using "single-side" deposition method as pervaporation membrane to separate 95% isopropanol/5%water mixtures. The pervaporation performance of PEMs prepared from salt solution was quite good with less than ten layer pairs. It was found that the separation factor a increased and the flux J decreased as the layer number increased, The adsorption of 6.5 layer pairs of PDDA/PSS at the presence of 0.75mol/L NaCl yielded the maximum flux of 1498g/m2h and the minimum separation factor of 247 when the feed temperature was 55"C. Both separation factor and flux increased with elevating operation temperature.更多还原