Abstract: Articles of commerce which are transparent at a first temperature and less transparent at a second temperature which is different from said first temperature and which are capable of reverting to the original state of transparency are obtained by curing compositions containing at least one isocyanate-functional monomeric or polymeric material which may or may not contain hydrophilic centers consisting essentially of ethylene oxide units having the structure (CH.sub.2 CH.sub.2 O).sub.n, wherein n is at least two. When the isocyanate-functional material does not contain such hydrophilic centers, it must be cured in the presence of at least one monomeric or polymeric material which may or may not be reactive with isocyanate groups but must contain such hydrophilic centers. Thermosensitivity is imparted to the cured products by the presence of water in the cured material.

Abstract: Articles of commerce which are transparent at a first temperature and less transparent at a second temperature which is different from said first temperature and which are capable of reverting to the original state of transparency are obtained by curing compositions containing at least one isocyanate-functional monomeric or polymeric material which may or may not contain hydrophilic centers consisting essentially of ethylene oxide units having the structure (CH.sub.2 CH.sub.2 O).sub.n, wherein n is at least two. When the isocyanate-functional material does not contain such hydrophilic centers, it must be cured in the presence of at least one monomeric or polymeric material which may or may not be reactive with isocyanate groups but must contain such hydrophilic centers. Thermosensitivity is imparted to the cured products by the presence of water in the cured material.