The solid-state degradation of poly(epsilon-caprolactone) catalyzed by
primary, secondary and tertiary alkylamines was investigated. The deg
radation process was monitored by weight loss and molecular weight cha
nge measured by gel permeation chromatography. Degradation studies wer
e conducted at 37 degrees C in methanol solutions of the alkylamines.
Primary alkylamines caused rapid weight loss (i.e., similar to 90% wei
ght loss in 30 days) that depended on alkylamine concentration, molar
ratio of alkylamine to poly(epsilon-caprolactone) monomer and alkyl ch
ain length. The secondary alkylamines caused less rapid polymer weight
loss (i.e., similar to 90%) weight loss within 80 days). One tertiary
alkylamine (N,N-diisopropylethylamine) showed little catalytic effect
while a bicyclic tertiary alkylamine (quinuclidine) was about as cata
lytic as the primary alkylamines. The degradation products isolated wh
en primary alkylamines were used include both esters and amides indica
ting that nucleophilic attack by the alkylamines competed with the ami
ne-catalyzed methanolysis reaction. Only ester moieties could be ident
ified in the products from reactions containing secondary and tertiary
alkylamines, which indicated that they acted as nucleophilic catalyst
s. All of the primary alkylamines reduced poly(epsilon-caprolactone) m
olecular weight from about 25,000 to 10,000 within 10 days after which
the molecular weight of the remaining solid leveled off even though w
eight loss continued.