We present a field-theoretic model to predict the equilibrium thermodynamic behavior of semiflexible diblock copolymers and random copolymers in the presence of solvent. Brie find that in both systems polymer-solvent contacts dramatically influence the thermodynamic behavior with decreasing the copolymer segment length (Lex molecular weight). When a copolymer has unequal, monomer composion , both polymer length and solvent concentration have a rong influence on the phase transition spinodal and magnitude of the critical wave modes: Diblock copolymers exhibit an expanded region of the lamellar phase in the phase diagram with decreasing chain length and polymer colleen, ion: Such effects suggest a breakdown, of the dilute approximation for solution of short diblock copolymers, Randam copolymer solutions also exhibit changes in the phase-transition spinodal and critical wave mode at asymmertric chemical compositions. This effect is highly relevant to most random copolymer material, since a minomer is typically a low-malecular weight chemical unit.