【作者】 吴伟泰；

【导师】 石磊； 朱清仁；

【作者基本信息】 中国科学技术大学 ， 凝聚态物理， 2008， 博士

【摘要】 本论文主要围绕如下三个方面的内容对刺激响应性高分子——聚乙烯醇缩丙酮（PVKA）及其衍生功能性材料进行研究:（1）具有特定目标的高分子合成:（2）探讨该高分子材料的性质:（3）利用这些性质制备功能性纳米材料。在这个思路指导之下所展开的研究工作可以概括如下:1.用对甲苯磺酸（PTS）和四丁基溴化铵（TBAB）作为催化剂,通过聚乙烯醇（PVA）与丙酮发生缩酮化反应,制备得到了PVKA。我们探讨了产物溶胀和溶解在氘代二甲基亚砜（DMSO-d₆）时的结构,实验结果同时也表明在溶解于水的过程中PVKA分子链上的缩酮环会发生半水解。我们探讨了反应温度、反应溶剂成分（DMSO和水的比例不同）、催化剂种类（CTAB、曲拉通）等反应条件对反应产物的缩酮化度（D_H,即对PVA的改性程度）的影响。与以前的实验方法相比,本实验方法具有可在一定程度上容忍水的存在、可获得具有较高缩酮化度的PVKA、产物的缩酮化度较容易控制等优点。据文献查询,这是首次在相转移催化条件下制备聚乙烯醇缩酮化物。这就为进一步深入研究PVKA的性质奠定了基础。2.PVKA是一种可水解的高分子,我们探讨了溶液pH值、温度、缩酮化度对PVKA的水解性的影响:当pH值越低,PVKA的水解较快;当pH值接近中性或者碱性时,PVKA的水解行为变得很缓慢,甚至几乎可以忽略;温度的提高有利于水解的进行;缩酮化度较高时,水解速率较慢。水解之后,PVKA变成PVA。当缩酮化度D_H在0.28至0.6范围时,PVKA在水溶液中表现出温度响应性相转变行为,其最低临界溶解温度（LCST）大致在33～45℃范围。我们还探讨了PVKA和TBAB缔合物,它们在由二甲基亚砜和丙酮组成的选择性溶剂中会发生自组装行为形成具有多种形貌的超结构。3.当水溶液中存在Ag⁺离子时,PVKA（D_H=0.533）的水解速率会大大加快,与此同时Ag⁺离子被还原形成具有多种形貌的金属Ag纳米结构。在PVKA（D_H=0.549）水溶液中,我们还通过金属Cu的自然氧化制备得到了Cu₂O多面体纳微米结构;在此过程中,PVKA的缩酮化度几乎没有发生改变,而可能起到了类似于催化剂的作用。4.作为上述研究工作的一个重要的延伸,我们利用PVKA的性质制备高分子/无机纳米复合材料,这些制备是在⁶⁰Coγ,射线辐照下进行的。PVKA中包含有刚性的六元缩酮环结构单元,其所造成的空间阻力会使得周围的乙醇结构单元变得相对“惰性”而不利于交联反应。随着PVKA在弱酸性环境中的缓慢水解,不断地缓解这种阻力,故可以在一定程度上减缓交联速率,并且会最终影响所得到的PVA的交联密度,从而有利于无机物在其中生长形成具有各种形貌。我们制备了Ag/交联PVA电缆状纳米复合材料、Ag/Cu₂O/交联PVA树枝状自组装体纳米复合材料、Ag/Cu₂O/交联PVA螺旋桨状自组装体纳米复合材料、Bi₂O₃/交联PVA纳米复合材料,探讨了反应机理、形貌形成机理,并探讨了材料的光学性质等。5.在⁶⁰Coγ射线辐照下,我们将PVA、PVKA共价接枝到多壁碳纳米管（MWCNTs）表面。我们还利用PVKA的pH值响应水解性质,依靠共价接枝在MWCNTs表面的高分子对金属Ag的亲合作用,有效地将金属Ag锚定在MWCNTs表面,制备得到了Ag/交联PVA/MWCNTs复合材料。Ag/交联PVA/MWCNTs复合材料是通过“一步法”制备得到的,即通过一次性实验从原料Ag⁺、PVKA和未经强酸处理的MWCNTs反应得到产物。据文献查询,这是首次在γ射线辐照下制备含有金属的高分子/碳纳米管复合材料。预期这种简单、有效的方法可以被推广到制备其它类似的基于CNTs的功能性复合材料。综上所述,本论文创造性地利用PVA的大分子反应特征,设计制备出缩酮化度可控的功能性高分子PVKA,从而调节其中两亲性结构单元（乙醇/缩酮环结构单元）比例来获得一系列具有相应功能化性能的材料,并且成功地延伸探讨了本论文各章中所描述的多种新型衍生功能性材料。更多还原

【Abstract】 In this dissertation,emphasis is placed on the investigation of polyvinylaceton （PVKA）,a stimuli-responsive polymer,and the derivative functional materials,which actually involves three main aspects:（1）the controllable synthesis processes to PVKA,（2）the characterization of the properties of the polymeric materials,and（3） the synthesis of the derivative functional materials utilizing the properties of PVKA. And the works under the guidance could be summarized as follows:1.With p-toluene sulfonic acid（PTS）and tetrabutylammonium bromide（TBAB） as the catalysts,PVKA was synthesized by ketalizing poly（vinyl alcohol）（PVA）with acetone.The structure of the product both swelled and dissolved in dimethyl sulfoxide-d₆（DMSO-d₆）was confirmed,which revealed the structural change in PVKA due to the semi-hydrolysis during its dissolution in water.Those effects,such as temperature,the composition of the reaction media（the ratio of water to DMSO）, the catalyst(e.g.CTAB and Triton^?X-100),and other conditions,on the ketalization degree（D_H,that is the modification degree of PVA）of the product were probed from experimental viewpoint.Compared with the literature method reported previously,the present method exhibites evident advantages,such as the bearing with water to some extent,the higher ketalized PVKA,the easier control on ketaiization degree,etc.This is the first time of report,to our best knowledge,that synthesizing polyvinylketal under phase transfer catalyst conditions.The present study may lead to a further investigate of attractive intrinsic properties of PVKA.2.PVKA is a hydrolysable polymer,whose hydrolysis time could be controlled by the pH value of water,temperature,and ketalization degree:the closer the pH value to neutral,the lower the hydrolysis rate;the elevated temperature favor hydrolysis;and the lower the initial ketalization degree,the more easily the hydrolysis proceeds in acidic water.The hydrolysis of PVKA leads to PVA.PVKA of D_H=0.28-0.6 exhibited temperature-induced phase transition in water,and the lower critical solution temperature LCST≈33～45℃.Moreover,we also investigated PVKA/TBAB complexes that generated a series of self-assembled superstructures in the selective solvent composed of DMSO and acetone.3.Further investigations found that the complete hydrolysis time of PVKA（D_H =0.533）could be greatly shortened in existence of Ag⁺,which would be simultaneously reduced to form Ag nanostructures of various morphologies.Cu₂O polyhedral micro/nanocrystals could also be synthesized in aqueous solution of amphiphilic PVKA（D_H=0.549）under ambient conditions,via natural oxidation of copper metal by naturally dissolved oxygen in water;however,herein PVKA possibly works as the role like catalyst,which changes the microenvironment for the electrochemical reaction,whilst the D_H keeps nearly the same.4.As an important extended research,the polymer/inorganics hybrid nanomaterials were synthesized under ⁶⁰Coγ-ray irradiation,utilizing the properties of PVKA.Because of the spatial interactions coming from the rigid six-membered ketal rings,which would make the neighbouring groups become unreactive,the low hydrolysis rate of the PVKA in dilute acidic solution hinders and then slows down the cross-linking of the PVA chains yielded,also resulting in a low cross-link density, which favors the growth of inorganics inside to form different structures.Those hybrids as Ag/cross-linked PVA cable-like nanohybrids,Ag/Cu20/cross-linked PVA dendritic assemblies,Ag/Cu₂O/cross-linked PVA propeller-like assemblies,and Bi₂S₃/Cross-linked PVA 3D dendritic nanohybrids were developed,and the proper explanation on both the reaction mechanism and the formation mechanism were proposed.Moreover,the optical and other properties were also explored.5.We developed an easy strategy of using ⁶⁰Coγ-ray irradiation to graft PVA and PVKA onto multi-walled carbon nanotubes（MWCNTs）without the use of aggressive acid treatment,all in a single processing step.We also tried to decorate MWCNTs with Ag nanoparticles relying on those covalently bonded polymers,via one-step covalent grafting of the polymer to the surface of MWCNTs,and simultaneous reducing of Ag⁺ ions to Ag which are then efficiently anchored onto the MWCNTs.This is the first time of report,to the best of our knowledge,that fabricating metalliferous polymer/CNT hybrids underγ-ray irradiation.It is envisioned that this simple but efficient method could be extended to fabricate other similar CNT-based hybrids.On summary,utilizing the character of the macromolecular reaction on PVA, PVKA of controllable ketalization degree was synthesized via ketaling PVA with acetone,in which the ratio of hydrophilic/hydrophobic structure units（alcohol/ketal ring units）was tunable and thus tailoring the properties of the founctional materials, and we also successfully extended our research to synthesizing a series of derivative functional materials as described in this dissertation.更多还原