Interpenetrating Polymer Networks and Related Topological Isomers
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Interpenetrating Polymer Networks and Related Topological Isomers
HARRY L. FRISCH Department of Chemistry,
State University of New York,
Albany, NY 12222
ABSTRACT
We have studied the phase compatibility of simultaneous interpenetrating polymer networks poly (2,6-dimethyl-l,4-phenylene oxide) with a number of other polymer networks as a function of their solubility parameters. Even when the blends of the corresponding linear chain polymers are immiscible their interpenetrating polymer networks can be miscible in all proportions. We have also prepared the corresponding pseudo (or semi) interpenetrating polymer networks where one component is linear and in one system the polymeric catenanes. All these systems generally show microphase separation.
1.
Introduction
Interpenetrating polymer networks (IPN's) are intimate mixtures of two or more crosslinked polymers, held together predominantly by permanent entanglements [1,21. IPN's can be prepared sequentially, i.e. by swelling one formed crosslinked network by the monomers (or prepolymers) crosslinking agents and initiators (or catalysts) of the other network (s) and subsequently polymerizing in situ. They can also be prepared simultaneously i.e. by mixing all the monomers (or prepolymers), crosslinking agents of the different networks, initiators and catalysts and polymerizing all at the same time. We will restrict ourselves here to simultaneous IPN's. Besides their interest as macromolecular topological isomers these materials allow one to produce more controlled and/or enhanced phase miscibility [3]. IPN's are often the only way of producing miscible alloys of crosslinked polymers. Besides depending on kinetic factors such as whether the half-life of formation of permanent entanglements in the IPNs is shorter than the half-life for phase separation due to "uphill diffusion" the extent of incompatability is dependent on thermodynamic factors such as the free volume change or the magnitude of the positive enthalpy of mixing found in
many systems.
The latter can be crudely estimated by means of the 6
6
solubility parameter [31 (6) or parameters [31 ( d, 6p, h) associated with the corresponding linear polymers. To see the effect of the latter we will focus on the properties of a number of recently synthesized simultaneous IPN's [A-9] in which one network consists of crosslinked poly (2,6-dimethyl-,14-phenylene oxide) (PPO) while the chemical nature of the other component will be varied. Related to the IPN's are the pseudo (or semi) IPN's in which only one component polymer of the mixture is crosslinked and the other component is left as a linear polymer (1,2]. Finally if one polymer is available as a sufficiently large ring then such rings can be permanently trapped in a different crosslinked polymer network forming a macromolecular catenane [10-121. We will briefly comment on these other macromolecular topological isomers of the PPO-IPN's.
Mat. Res. Soc. Symp. Proc. Vol. 171. (;1990 Materials Research Society
232
2.
PPO-IPN's
PPO can be conveniently cro
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