Aging effect molecular motion

Solid-state NMR methods have been much used to study the characteristics of the network chains themselves, particularly with regard to orientations [265], molecular motions [266], and their effects on the diffusion of small molecules [267], Aspects related to the structures of the networks include the degree of cross-linking [268,269], the distributions of cross-links [270] and stresses [271], and topologies [272,273]. Another example is the use of NMR to clarify some issues in the areas of aging and phase separation [274],... 

The influence of temperature and strain rate can be well represented by Eyring s law physical aging leads to an increase of the yield stress and a decrease of ductility the yield stress increases with hydrostatic pressure, and decreases with plasticization effect. Furthermore, it has been demonstrated that constant strain rate. Structure-property relationships display similar trends e.g., chain stiffness through a Tg increase and yielding is favored by the existence of mechanically active relaxations due to local molecular motions (fi relaxation). 

The objective of this investigation is to describe the effect of physical aging on the molecular motion of the membranes of PMSP and poly(l-trimethyl-l-propyne-co-1-phenyl-1-propyne) [poly(TMSP-co-PP] and blend polymer of PMSP with poly(l-phenyl-1-propyne) (PPP). 

Effect of aging on the permeability and molecular motion of the membranes of PMSP, poly(TMSP-co-PP) and blend of PMSP/PPP Glassy polymers, such as PMSP, are nonequilibiium materials and their permeation and sorption properties drift over time as thermally driven, small-scale polymer segmental motions cause a relaxation of nonequilibrium excess free volume. The microcavities of large size which are present in PMSP membrane have been considered to be responsible for the decay of C h and the gas permeability (4). Therefore, it is possible to stabilize the gas permeability by control the C by copolymerization or blending with the other acetylene derivatives such as PP and PPP, respectively. 

Effects of Physical Aging on Gas Permeability and Molecular Motion in Poly(l-trimethylsilyl-l-propyne)... 

The catalyst used for polymerization influences several properties such as the solubility of PTMSP in various solvents (7). Even though the cis-trans content of PTMSP has not been quantitatively determined, Costa et al (5) and Izumikawa et al. (6) reported that the polymerization catalyst NbClj produced a more regular chain confi ation than TaClj. In addition, PTMSP synthesized using NbClj had a cis-rich structure relative to that prepared with TaClj. In this study, Sie effects of physical aging on gas permeability and molecular motion of PTMSP membranes synthesized using various catalysts are reported. 

Arrhenius plots demonstrating the effect of temperature on lettuce seed aging rate (squares) and on molecular mobility calculated using the Adam-Gibbs model and heat capacity measurements (open circles) and from rotational motion using electron spin resonance measurements. Data are from Walters et al., (2004) (aging rate), Walters, (2004) (glass relaxation rates) and Buitink et al., (2000) (ESR measurements). 

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