Phase Behavior of Polystyrene-block-Poly(n-butyl-ran-n-hexyl) Methacrylate Copolymers

• Published in: Macromolecules Vol. 41; no. 18; pp. 6793 - 6799
• Main Authors: Moon, Hong Chul, Han, Sung Hyun, Kim, Jin Kon, Li, Guang Hua, Cho, Junhan
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 23.09.2008
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties; Terpolymer; Monodispersed polymer; Pressure effect; Alkyl methacrylate copolymer; Diblock copolymer; Order disorder transformation; Experimental study; Butyl methacrylate copolymer; Molecular weight property relation; Styrene copolymer; Transformation temperature
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma800645u

The phase behavior of symmetric polystyrene-block-poly(n-butyl-ran-n-hexyl) methacrylate copolymers (PS-b-Pn(B-r-H)MA) with various molecular weights was investigated by small-angle X-ray scattering (SAXS), rheometry, polarized optical microscopy (POM), and static birefringence. PS-b-PnBMA exhibited a lower disorder-to-order transition (LDOT), whereas PS-b-PnHMA exhibited an order-to-disorder transition (UODT). However, when a random copolymer of Pn(B-r-H)MA was used as one of the blocks, PS-b-Pn(B-r-H)MA showed closed-loop phase behavior having both LDOT and UODT, which was seen in PS-b-poly(n-pentyl methacrylate) copolymer, when the total molecular weight was judiciously controlled. The phase behavior change by including a random copolymer was explained by an argument based on a compressible random phase approximation. We also found that the pressure coefficient of both transition temperatures of PS-b-Pn(B-r-H)MA was much larger than that of neat PS-b-PnBMA and PS-b-PnHMA.