P(VDF-co-TrFE-co-CTFE)-g-SPS共聚物的合成表征

采用商业聚(偏氟乙烯-co-三氟氯乙烯)(P(VDF-co-CTFE)为原料,结合氢化反应、ATRP和磺化反应系统合成了一系列聚(偏氟乙烯-co-三氟乙烯-co-三氟氯乙烯)-g-磺化聚苯乙烯(P(VDF-co-TrFE-co-CTFE)-g-SPS)共聚物.重点研究了测试环境(如温度和相对湿度)、聚合物微观结构(接枝密度,接枝长度等)对聚合物形貌、吸水率和质子传导率的影响.研究表明,在接枝量相同的情况下,随着接枝密度的降低,聚合物的相分离更加明显,亲水相从孤岛型逐渐转变为部分连续型;聚合物的吸水率随磺酸基摩尔含量增加而提高;聚合物的质子传导率随着温度的提高和湿度的降低而降低;在较低温度下,聚合物的电导率随接枝密度的增加而降低,而在较高温度下,聚合物的电导率随接枝密度的增加而升高.组成优化的P(VDF-co-TrFE-co-CTFE)-g-SPS共聚物在30～120℃和高湿度条件下,其质子传导率明显优于Nafion112膜.

SYNTHESIS AND CHARACTERIZATION OF P ( VDF-co-TrFE-co-CTFE ) -g-SPS

Proton exchange membrane fuel cells (PEMFC) have attracted considerable research interest for its advantages in cleaning energy such as no pollution and no warm house gas. Although the mostly investigated Nafion series products possess excellent properties,their low conductivity at high temperature and low humidity as well as their high cost is still limiting their application. In this work,a series of poly( vinylidine fluorde-cotrifluroethylene-co-chlorotriflurethylene)-g-sulfonated polystyrene P(VDF-co-TrFE-co-CTFE)-g-SPS) copolymers with tunable graft densities and branch lengths are synthesized using commercial P ( VDF-co- CTFE) via a route including partial hydrogenation,ATRP and sulfonation reaction. The structure and properties of these polymers are carefully characterized with NMR,TEM,water uptake and proton conductivity measurement. The influence of test condition and polymer construction on their properties has been well discussed. It has been shown that the graft density governs the phase separation of the resultant polymer,and therefore its water uptake and proton conductivity. The copolymer with low graft densities shows larger scale phase separation,higher water uptake and larger conductivity at low temperature. As temperature increases,the proton conductivity of the copolymer with low graft density increases. The copolymer with optimized composition exhibits even higher proton conductivity than that of Nafion-112 tested at a relative humidity over 50% in the same condition,temperature range 30 ～ 120℃ . Therefore,it is expected to be an excellent PEM materials with low cost.