K. Schäler, E. Ostas, K. Schröter, T. Thurn-Albrecht, W. H. Binder, K.
Influence of Chain Topology on Polymer Dynamics and
Crystallization. Investigation of Linear and Cyclic
Poly(ε-caprolactone)s by 1H Solid-State
Macromolecules 44, 2743–2754 (2011). DOI 10.1021/ma102838c.
We report on the investigation of cyclic and comparable linear
poly(ε-caprolactone)s (PεCL) with molecular weight between 50
and 80 kg/mol with regard to chain mobility in the melt and crystallinity using
low-field solid-state 1H NMR. Our results from
NMR Hahn echo and more advanced multiquantum measurements demonstrate a higher
segmental mobility of cyclics in the melt as compared to their linear
counterparts. Rheological experiments indicate that the cyclics are less viscous
than the linear analogues by about a factor of 2, confirming the NMR results.
FID component analysis shows higher crystallinities of the cyclic samples by
some percent under the condition of isothermal crystallization at 48 °C,
suggesting that due to their enhanced overallmobility in the melt, the cyclics
reach amore perfect morphology leading to higher crystallinity. We compare this
finding with results from DSC measurements obtained under identical conditions
and critically evaluate the applicability of polymer crystallinity determination
from nonisothermal crystallization investigations by DSC. We further highlight
the use of nucleating agents to investigate the particular effect of crystal
growth on (nonisothermal) crystallization, separated from the influence of
nucleation. These experiments indicate a faster crystal growth for cyclic