Polyethylene oxide temperature - or fluid-sensitive shape memory device
AssigneeNational Research Development Corporation
InventorsNeil B. Graham, Marion E. McNeill
Life of this patent
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Abstract
A temperature- and/or polar fluid-sensitive device which comprises a mechanically strained semi-crystalline hydrophilic polymer.
Claims5
A device which changes its shape when its temperature is increased above a threshold level or when it has its surface contacted by a polar fluid, in which the device is made of a shaped body of material which comprises a chemically cross-linked, water-insoluble, hydrophilic polymer having polyethylene oxide units, said units having a number average molecular weight (M.sub.n ) of from 1,500 to 12,000, which polymer has in it regions of crystalline material of which the crystallite melting temperature (T.sub.m) lies in the range from -10.degree. C. to 70.degree. C., and in which the body has been mechanically strained to a deformation ratio in the range of 1.1 to 10 prior to its being heated or exposed to a polar fluid, being retained in its strained shape solely by internal forces which may be reduced or removed to permit the device to resile towards its unstrained shape.
A process for the preparation of a device which changes its shape when its temperature is increased above a threshold level or when it has its surface contacted by a polar fluid, which comprises the steps of:
- 1) subjecting a shaped body of material which comprises a chemically cross-linked, water-insoluble, hydrophilic polymer having polyethylene oxide units, said units having a number average molecular weight (M .sub.n ) of from 1500 to 12000, which polymer has in it regions of crystalline material of which the crystallite melting temperature (T.sub.m) lies in the range of from -10.degree. C. to +70.degree. C., to a stress causing it to be mechanically strained to a deformation ratio in the range of 1.1 to 10;
- 2) effecting the deformation at a temperature at or above T.sub.m and
- 3) cooling the strained body to a temperature below T.sub.m while maintaining the deforming stress on it.
Dependencies are inferred from the claim text.