Thermostropic biphilic hydrogels and hydroplastics
AssigneeCiba-Geigy Corporation
InventorKarl F. Mueller
Life of this patent
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Abstract
Novel hydrogels and hydroplastics are described which exhibit temperature dependent, reversible phase separations and clear-opaque transitions between 1.degree. and 100.degree. C. These materials consist of linear or crosslinked random copolymers of N,N-dimethylacrylamide with alkyl- and alkoxyalkyl acrylates. The water solubility and water swelling of these polymers is extremely temperature dependent; they show sharply defined clear to opaque transitions in their water swollen state and as soluble polymers shown Lower Critical Solution Temperatures (LCST). They are useful in drug delivery systems, absorption and extraction processes and as qualitative thermometers, thermosensors and self-activating sunscreens, for example in greenhouses.
Claims19
A random copolymer which in its water-equibrated state has a thermoreversible transition between 1.degree. and 95.degree. C. and which comprises the copolymerization product of:
- (a) 20 to 85% by weight of N,N-dimethylacrylamide;
- (b) 15 to 80% by weight of an aliphatic, cycloaliphatic, aromatic or alkaromatic hydrocarbyl acrylate with 1 to 18 carbon atoms in the hydrocarbyl moiety, or an alkoxy- or poly(alkoxy)ethyl acrylate with 2 to 5 carbon atoms in the alkoxy moiety, or mixtures thereof,
- (c) 0 to 5% by weight of a polyolefinic crosslinking monomer, and
- (d) 0 to 20% by weight of one or more monoolefinic monomers other than the acrylates of component (b),
- with the proviso, that if component (c) is greater than zero, component (d) is zero and component (a) is 20 to 55% by weight and the equilibrium water content of the crosslinked polymer is 12 to 55% by weight of the swollen gel, and with the further proviso that if component (b) is methyl, ethyl, propyl or butyl acrylate, the polymer is uncrosslinked (c=zero).
Dependencies are inferred from the claim text.