phase domain of microscopic or smaller size, usually in a block, graft, or segmented copolymer, comprising essentially those segments of the polymer that have glass transition temperatures lower than the temperature of use.
Note:
Soft-segment phase domains are often larger than hard-segment phase domains and are often continuous.
Source:
PAC, 2004, 76, 1985. 'Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)' on page 2002 (https://doi.org/10.1351/pac200476111985)