Study On The Preparation Of Polyacrylamide And The Mechanisms Of Hofmann Reaction

The synthesis of the low-molecular-weight polyacrylamide (PAM)was investigated in the mixed solvents of ethanol and acetone .The monomer conversion was 97% in short time . The low-molecular-weight polyacrylamides (viscosity-average molecular weight =2.0 104-24.0 104) were obtained by changing the weight ratio ethanol to acetone or the acrylamide concentration.The Hofmann reactions of five polyacrylamides(PAM) with different molecular weights under two different concentrations were carried out to get better understanding of mechanisms of the reaction . The results show that the maximum conversion of N-Chloroamides increased with molecular weights of PAM, and got to the highest point at 9.0 104, then decreased . The changes in maximum conversion of amino groups resemble those of N-Chloroamides, the maximum degree of amino group of PAM in the study was 97%. However , the time to reach maximum conversion of amino groups appeared to be independent of the molecular weights in the range investigated.A series of acrylamide-styrene copolymer latices with different acrylamide and styrene weight ratio were prepared from the polymerization in emulsifier-free aquesous media .The latices were stable ,thixotropic and monodisperse .The particle sizes range from192 to 94 nm depending on the acrylamide fractions. The Hofmann reactions of these latices were carried out to introduce primary amines on the particle surface.The reaction stages in the emulsion were similar to that in the aquesous solution.The amount of amine groups formed increased with the acrylamide fraction to 81.0%,as f=0.60,then decreased.The particle sizes were smaller ,and the size distributions were worse compared with latices without degradation.