Premium
CIDNP.‐Investigation of Photoinduced Polymerization
Author(s) -
Borer Armand,
Kirchmayr Rudolf,
Rist Günther
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610127
Subject(s) - chemistry , cidnp , radical , acetophenone , photochemistry , polymerization , monomer , cationic polymerization , radical polymerization , bulk polymerization , polymer chemistry , polymer , organic chemistry , catalysis
The photochemistry and some initiator characteristics of the polymerization initiators ω,ω‐dimethoxy‐ω‐phenyl‐acetophenone ( A ), ω,ω‐diethoxy‐acetophenone ( B ) and ω,ω‐diisopropoxy‐acetophenone ( C ) have been studied by 1 H‐ and 13 C‐chemically‐induced nuclear polarization (CIDNP.) experiments. The primary reaction of initiator A is a Norrish ‐type I cleavage, while for B and C Norrish ‐type I and Norrish ‐type II cleavages are of comparable importance. Three different recombination products could be detected for initiator A which correspond to the three canonical resonance forms of the substituted benzyl radical. In a number of polymerization experiments the competition between reactions among initiator radicals and reactions of initiator radicals with the monomer acrylic acid methyl ester was studied at low concentrations of the monomer. These experiments give insight into the first steps of the polymerization process. The positive sign of the α‐hydrogen hyperfine couplings of the dimethoxy‐methyl‐ and the diisoproproxymethyl‐radicals could be established, in agreement with the deviation of these radicals from planarity. A slow square‐wave light‐modulation technique has been employed in 13 C‐FT.‐experiments to measure absolute CIDNP.‐intensities.