Pastukhov A.V., Tsyurupa M.P., Davankov V.A. Hypercrosslinked polystyrene: a polymer in a non-classical physical state

J. Polymer. Sci., Part B: Polym. Phys. 1999. V.37. P.2324-2333.

Hypercrosslinked Polystyrene: A Polymer in a Non-ClassicalPhysical State

ALEXANDER V. PASTUKHOV, MARIA P. TSYURUPA, VADIM A. DAVANKOV

Nesmeyanov Institute of Organo-Element Compounds, Russian Academy of Sciences,117813 Moscow, Russian Federation

Received 15 June 1998; revised 23 February 1999; accepted 15 April 1999

ABSTRACT: Deformation and relaxation properties of hypercrosslinked polystyrenenetworks have been studied by thermomechanical method at a uniaxial compressionusing individual spherical beads of the polymer. The networks examined were preparedby postcrosslinking of highly swollen beads of a styrene-0.3% DVB copolymer with0.3–0.75 mole of monochlorodimethyl ether, which results in the introduction of 0.6–1.5methylene bridges between each two polystyrene phenyl rings. The polymers obtainedare shown to belong neither to typical glassy materials, nor to typical elastomers.Though no characteristic plateau of rubberlike elasticity was observed on the deforma-tion curves of the beads, the polymers exhibit two fundamentally important features ofthe rubberlike state: The deformations are large (up to 30–40% of the initial diameter)and reversible. Relaxation of residual deformations, however, requires prolonged heat-ing of the sample, or a cycle of swelling and drying. The deformation can start in thetemperature range from 270 to 1150°C depending on pressure applied. The crosslink-ing degree in the range from 40–100% and higher does not affect noticeably thebehavior of the hypercrosslinked polystyrene. Nature of the high mobility of the hyper-crosslinked network is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys37: 2324–2333, 1999Keywords: hypercrosslinked polystyrene; thermomechanical curves; deformation;relaxation; physical state of polymers

INTRODUCTION

Three physical states, glassy, rubberlike (or rub-bery) and viscous-flow states, are well known to becharacteristic of amorphous linear high molecularweight polymers.1,2 The transition of polymers fromone state to another proceeds in response to chang-ing temperature which affects the accumulatedheat energy of macromolecules and, therefore, theirmobility. Introduction of crosslinks between linearchains of the polymer restricts the chain mobility,which manifests itself in the elimination of the vis-cous-flow state and the shift of the glass transition

temperature, Tg, towards higher values. If the net-work was prepared in the absence of any solvent,the entrapped entanglements or, which is the same,interpenetration of network meshes are so signifi-cant that even a moderate amount of chemicalcrosslinks can fully deprive the network of becom-ing elastic up to the temperature of chemical deg-radation. In styrene-DVB copolymers, such an elim-ination of the rubberlike state takes place at theDVB content of above 25%. Concomitantly, such apolymer does not swell with solvents, at all. How-ever, a network does not necessarily need to lose itsmobility with increasing crosslinking degree, if theconditions for the preparation of the network areselected in such a manner as to substantially reducethe interpenetration of the network meshes formedin the process of crosslinking.

Correspondence to: A. V. Pastukhov (E-mail: davank@ineos.ac.ru)Journal of Polymer Science: Part B: Polymer Physics, Vol. 37, 2324–2333 (1999)© 1999 John Wiley & Sons, Inc. CCC 0887-6266/99/172324-10

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