聚4-乙烯基吡啶原位修饰PVDF膜及其负载磷钨杂多酸催化剂的研究

Immobilization of Phosphotungstic Acid Catalysts on PVDF Membranes in situ Modified by Poly(4-vinylpyridine)

以聚偏氟乙烯(polyvinylidene fluoride,PVDF)微滤膜为基膜,4-乙烯基吡啶(4-vinylpyridine,4VP)为功能单体,采用表面引发电子活化再生原子转移自由基聚合(SI-AGET ATRP)法在基膜表面原位改性,并通过接枝聚合物侧链上的吡啶基团与Keggin型磷钨杂多酸(H3PW12O40·n H2O,HPW)之间的静电作用,制备了新型混合催化膜.实验结果表明,接枝聚合过程表现出"活性"/可控表面引发接枝聚合性质,基膜表面接枝聚合物量随聚合反应时间呈现线性增加,当反应时间为16 h,聚合物接枝量达到2.25 mg/cm2,聚合物接枝量的增多致使其相互堆积并坍塌,造成膜表面出现块状聚集体.然后,利用溴代十六烷对接枝聚合物进行季铵化改性,制得表面含有吡啶鎓盐的阳离子复合膜,通过接枝聚合物侧基中的吡啶和吡啶鎓盐基团与磷钨杂多酸之间的静电作用促使其在改性膜表面上有效负载.负载后的磷钨杂多酸均匀的分布在膜表面及孔道中,并保持其化学结构.负载催化剂前后膜的接触角从80.4°减小到57.8°,体现了亲水性催化剂的负载对膜表面润湿性的显著影响.

Polyvinylidene fluoride（ PVDF） membranes as supports were in situ modified by surface-initiated electronic activation of regeneration atom transfer radical polymerization（ SI-AGET ATRP） of 4-vinylpyridine（ 4VP） functional monomer. The pyridine pendant groups at the grafted P4 VP side-chains were in turn entrapped with Keggin-type phosphotugnstic acid（ H3PW12O40·n H2 O,HPW） catalysts on modified membranes via electrostatic interaction to prepare a novel hybrid catalytic membrane. The results of the polymerizations demonstrated the features of ＂living＂/ controlled surface-initiated grafted polymerization and the grafted yields of poly（ 4-vinylpyridine）（ P4VP） linearly increased with polymerization reaction times. The grafted yields reached to 2. 25 mg / cm2 when the polymerization time was 16 h. And the same time,the lumpy structure aggregation appeared on the surface of modified membranes by reason of the collapse of tightly packed grafted P4 VP with high grafted yields. Subsequently,the quaternization of the grafted P4 VP with bromohexadecane was carried out to create the cationic composite membranes,containing dense and reactive quaternary ammonium pyridine groups. The pendant pyridine and pyridinium groups facilitated the electrostatic assembly of HPW onto the P4VP-grafted membranes. Supported-HPW catalysts were homogeneously loaded on the PVDF-g-QP4 VP membrane surface and pores and maintained the primary Keggin structure. The water contact angles values of PVDF-g-QP4 VP / HPW catalytic membranes decreased from 80. 4° to 57. 8°,this result exhibited the significant effect on the wettability of membranes through loading the hydrophilic catalysts.