電漿改質PNIPAAm-g-PVDF熱響應薄膜特性研究

Abstract

Poly(N-isopropylacrylamide) (PNIPAAm) was successfully grafted on the surface of poly(vinylidene fluoride) (PVDF) membranes by plasma induced post- graft polymerization method. A series of thermoresponsive grafting membranes with a wide range of grafting degree was prepared. The effect of the grafting degree on the thermal response characteristics was investigated. ATR-FTIR and XPS elemental analysis confirmed that the grafting reaction was successful and the functional group in PNIPAAm (C=O, -NH) was retained. The effect of plasma power, monomer concentration and grafting time on grafting degree was investigated. Results showed that the grafting degree increased with increasing the monomer concentration and grafting time. From SEM observation, the surface coverage of PNIPAAm was increased with the increase in grafting degree. Results of water contact angle measurement and pure water permeation test showed that PNIPAAm-g-PVDF had a good thermal responsibe.The PNIPAAm polymer chain was shrink and exhibited a hydrophobic character when the temperature was higher than LCST; lower than the LCST,it was stretched and showed a hydrophilic behavior. When the grafting degree increased, the thermal response of PNIPAAm chain first increased than decreased. The higher the grafting degree the stronger the response of PNIPAAm. However, the pores were plugged by the PNIPAAm chain when the grafting degree was too high and resulted in shrinking or stretching the PNIPAAm chain . In drug delivery, and the results match with water permeation test, the GD = 10.1%, have the best thermal response property. By using positron annihilation lifetime (PALS) analysis, the free volume in PNIPAAm-g-PVDF membrane showed a bimodel distribution when T>LCST. This result could be related to the shrinking behavior of the PNIPAAm polymer chain.