Studies On Silk Grafting Using Acrylate Monomers Via ATRP Method In Aqueous Medium

In order to improve the properties of silk, silk was grafted using living polymerization, atom transfer radical polymerization(ATRP), in aqueous medium. The reactivity and reaction conditions of acrylate monomers were discussed in silk grafting. The structure and properties of grafted silk were studied and silk with good bacteria repellancy and crease resistance was obtained.Silk macroinitiator was prepared using 2-bromoisobutyryl bromide (BriB-Br) as initiator, 4-dimethylamino-pyridine(DMAP) as catalyst, and triethylamine(TEA) as acid-binding agent. The effects reaction conditions on Br content of silk macroinitiator were discussed and the optimal reaction condition was obtained. Br content of silk macroinitiator measured by energy spectrum was 1 (Wt%),and quantitatively measured by ion chromatography after oxygen flask combustion was measured was 0.032(Wt%). X-ray photoelectron spectroscopy(XPS) indicated that Br was introduced onto the surface of silk by covalent bond and silk macroinitiator was successfully prepared.Silk fabrics were grafted using dimethylaminoethyl methacrylate (DMAEMA), diethylaminoethyl methacrylate (DEAEMA) and dimethylaminoethyl acrylate (DMAEA) as monomers. The reactivity of the three monomers was compared in silk grafting using conventional chemical initiation and ATRP methods. It was found that the three monomers were much easier to be grafted onto silk by ATRP method than by conventional chemical initiation method, and better grafting result could be obtained using ATRP method. Accordingly, a new feasible method was developed for those monomers not suitable for silk grafting by conventional chemical initiation method, and some research bases were established.The effects of monomer concentration, dosage and ratio of catalyst and ligand, reaction temperature and time on silk grafting using three nitrogen containing monomers were discussed and optimum grafting reaction conditions were obtained. It was confirmed that the ATRP grafting displayed"living"characteristics. DMAEMA grafted silk by ATRP method could be re-grafted by a monomer, dimethyl methacryloyloxyethyl phosphate, with flame retardant property. Thus, silk with multi-function could be developed via ATRP method.Silk fabrics were grafted using hydroxyethyl methacrylate(HEMA), hydroxyethyl acrylate(HEA) and hydroxypropyl methacrylate(HPMA) as monomers. The reactivities of the three monomers were compared in silk grafting using conventional chemical initiation and ATRP methods. It was found that the three monomers were much easier to be grafted onto silk by conventional chemical initiation method than by ATRP method. The grafting techniques of the three monomers were discussed and the optimum grafting conditions were obtained.Attenuated total reflectance-Fourier transform infrared spectroscopy(ATR-FTIR) and Raman spectra of grafted silk by ATRP method indicated that the monomers were grafted onto silk fabrics, and the grafted silk still mainly appearedβ-sheet conformation. X-ray diffraction of grafted silk showed that the grafting mainly occurred at amorphous region of silk not crystalline region. XPS of grafted silk indicated that monomers were grafted onto silk fabrics. It could be observed from images of scanning electron microscope(SEM) and atomic force microscope(AFM) that the surface roughness of silk fabric increased with the grafting yields increasing, however, the silk surfaces were still smooth and even.The DSC result showed that the thermal stability of grafted silk increased with the grafting yields increasing. The moisture regain of grafted silk almost didn't change, whiteness, breaking strength, handle and air permeability of grafted silk slightly decreased, which didn't affect the wearability and other properties.The bacteria repellancy quantitative analysis result of quaternized silk grafted by three nitrogen containing acrylate monomers wasobtained. The bacteria repellency of DEAEMA grafted silk was the best, the followed was DMAEMA grafted silk, and the worst was DMAEA grafted silk. The bacteria repellency of silk increased with the increase of alkyl chain length of quaternary ammonium monomers. The bacterial inhibition of three monomer grafted silk to S. aureus was better than to E. coli. And the bacteria repellency of three nitrogen containing acrylate monomers grafted silk had good washing durability.The dry and wet crease recovery of three hydroxyl containing monomers grafted silk was both improved, and the wet crease recovery was improved significantly. The wet crease recovery of grafted silk increased with the increase of grafting yields.