Topic 6	Abstract No.PB37
PULSED NMR STUDY ON BULK POLYMERIZATION OF ACRYLIC ACID, METHYL ACRYLATE AND 2, 2, 2 -TRIFLUOROETHYL ACRYLATE
T. Kurotsu^a, A. Fukuda^a, H. Kimoto^a, A. Asano^a and Ch. M. Sullivan^b
^aDepartment of Applied Chemistry, TheNational Defense Academy, Yokosuka 239-8686, JAPAN, ^bprevious address: Cancer Research Institute, The University of California, San Francisco, CA, 94097, USA
Bulk polymerizations proceed with a phase transition from liquid state to solid one through gel state. We measured ^1H spin-spin relaxation times (T2) of acrylic acid (AA), methyl acrylate (MA) and 2,2,2,-trifluoroethyl acrylate (FEA) as a function of the polymerization time?@to analyze the relation between the fraction of T2 and the polymer yield. Three kinds of relaxation times (T2l) (long), T2s (short) and T2m (intermediate) corresponding to the difference in molecular motion were observed as the polymerizations proceeded. The fraction of T2s component (Fs) increased like in “Trommsdorff effect“ while that of T2l (Fl) decreased. The time course of Fs for AA, MA and FEA almost corresponds to the polymer yield except for the early stage of the polymerizations. The phase transition through gel state is caused by a formation of three dimensional entanglement (network structure) of the polymer chains. This entanglement decreases the polymer chain mobility. The network structure of AA is much likely to occur becasue AA has carboxylate groups (COOH) in its side chain to cause an association of COOH in addition to the main chain entanglement. The entanglement for AA enables us to detect Fs componet even in the early stage of polymerization. The time course of Fs for AA is, therefore, more silmilar to that of polymer yield than MA because of this easiness of a formation of the network structure. The effect of different kinds of side chain on the network formation was also examined by ^19F resonance of side chain of FEA.