氢键复合膜在酸性溶剂中溶解研究

Disassociation of Hydrogen-bonded Polymer Complex Thin Films in Acidic Solvents

以聚乙烯吡咯烷酮(PVPON)、聚丙烯酸(PAA)分别为氢键受体和氢键给体,利用层层组装技术制备高分子氢键复合膜.利用紫外-可见光谱、红外光谱及原子力显微镜研究了PVPON/PAA氢键复合薄膜在甲酸、三氟乙酸、磷酸、多聚磷酸中的解离过程.氢键复合薄膜在酸性溶剂中解离速率的快慢为三氟乙酸>磷酸>甲酸.在不同的酸性溶剂中,氢键复合膜的解离机理不同.三氟乙酸体系主要与薄膜中的PAA发生作用,致使PAA与PVPON之间的氢键解离,从而薄膜溶解.而磷酸和多聚磷酸体系则主要与PVPON发生作用,使薄膜溶解.多聚磷酸与磷酸相比,具有更多质子给体基团,与PVPON作用是体现出协同效应.甲酸和PAA同属于羧酸,甲酸分子很难取代PAA,与PVPON形成氢键,其溶解速度非常缓慢.

The hydrogen-bonded films were prepared via layer-by-layer assembly of poly（ vinylpyrrolidone）（ PVPON,hydrogen bond acceptors） and poly（ acrylic acid）（ PAA,hydrogen bond donors）. UV-Visible spectra,FTIR spectra and AFM were used to investigate the hydrogen bond detachment and the film disintegration in acidic solvents： formic acid,trifluoroacetic acid,phosphoric acid and poly（ phosphoric acid）.The dissolution rate of the PVPON / PAA thin film in different acids was queued as： trifluoroacetic acid phosphoric acid formic acid. The experimental results indicated that the mechanism of hydrogen bond detachment was not the same in different acids. Trifluoroacetic acid shows strong interaction with PAA,which induces the detachment of hydrogen bonds between PVPON and PAA,and thus the PVPON / PAA film dissolves. However,phosphoric acid or poly（ phosphoric acid） has strong interaction with PVPON,which makes hydrogen bonds between PVPON and PAA break and the thin film decomposes. Poly（ phosphoric acid） has more hydrogen bonding donor groups than phosphoric acid,and hence the interaction between poly（ phosphoric acid） and PVPON exhibits an synergetic effect. Formic acid and PAA both belong to the family of carboxylic acids. It is very hard for formic acid to replace PAA to form hydrogen bond with PVPON,and hence the film dissolution rate in formic acid is very low.