On the entanglement density of differently N-substituted alternating styrene-maleimide copolymers

Differently N-substituted maleimides were copolymd. with styrene to yield alternating styrene-maleimide copolymers (SMI-R) with different chain diams. The polymers were obtained by free radical polymn. and characterized by NMR and size exclusion chromatog./differential viscometry. Glass transition temps. were measured by differential scanning calorimetry. An increase in chain diam. and chain stiffness is accompanied by a decrease in the entanglement d., reflected in lower values of the plateau modulus, which were cor. for the low mol. wt. portion using the Wasserman/Graessley model. Increasing the chain diam. by a factor of two results in a decrease of the entanglement d. to one third. SMI-Me showed a much lower entanglement d. than polystyrene (PS) although they have the same chain diam. SMIMe however is more rigid than PS because of the maleimide five-membered ring structure in the main chain. SMI-Me and SMI-PhOPh show the same glass transition temp. However, because of the larger chain diam. of SMIPhOPh, it has a much lower entanglement d. Thus, both the chain flexibility and the chain diam., two parameters that are strongly related, affect the entanglement d. [on SciFinder (R)]