Abstract: There are provided composites having near-zero uniaxial thermal expansion coefficients. One or more polyacetylenes having a negative uniaxial thermal expansion coefficient are uniaxially or biaxially oriented within one or more solid matrix materials having a positive thermal expansion coefficient to yield a composite material having a uniaxial thermal expansion coefficient which is nearly zero. The polyacetylenes are obtained by the solid-state polymerization of crystals of monomers containing at least one --C.tbd.C--C.tbd.C-- grouping per molecule. Also provided are processes for producing the above-described composites.

Abstract: There are provided processes and compositions for obtaining organic polymeric materials having near-zero uniaxial thermal expansion coefficients. According to one embodiment, an organic polymer having a negative uniaxial thermal expansion coefficient is treated by thermal processing under conditions sufficient to cause at least a portion of the polymer chains to become misaligned, thereby decreasing the magnitude of this thermal expansion coefficient to nearly zero. According to a second embodiment, one or more organic polymers having a negative uniaxial thermal expansion coefficient are combined with one or more materials having a positive thermal expansion coefficient to yield a composite material having a uniaxial thermal expansion coefficient which is nearly zero.