Chemical Substituent Effects on Morphological Transitions in Styrene−Butadiene−Styrene Triblock Copolymer Grafted with Polyhedral Oligomeric Silsesquioxanes

Abstract

A series of hybrid organic/inorganic triblock copolymers of polystyrene-butadiene-polystyrene (SBS) grafted with polyhedral oligomeric silsesquioxane (POSS) molecules with different chemical constituents were synthesized by a hydrosilation method. Four POSS macromers, R′R 7 Si 8 O 12 , were designed to contain a single silane functional group, R′, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block and seven identical organic groups, R. Small-angle X-ray scattering and rheological techniques were used to study the effect of sterically similar, yet electronically different, organic R groups, cyclopentyl (Cp), cyclohexyl (Cy), cyclohexenyl (Cye), and phenyl (Ph), on the morphology of SBS triblock copolymer and the order-disorder transition behavior. It was observed that POSS with phenyl moiety, when grafted to the polybutadiene (PB) phase, appears to show favorable interaction with the polystyrene (PS) phase; effectively, the Ph-POSS is plasticizing the SBS due to an effect whereby the Ph-POSS is at least partially solvated by the PS phase. This causes a significant decrease in the overall lamellae d spacing and the order-disorder transition temperature, T ODT , with increasing amounts of Ph-POSS attachment. As we change the POSS moiety to that of Cye, Cy, and Cp, the interaction between POSS-PS weakens, and the d spacing and T ODT become less dependent on the amounts of POSS attachment. At the highest POSS loadings investigated (20 wt %), there is a change to a perforated layer morphology, resulting in an increase of T ODT relative to the 10 wt % POSS-grafted copolymers for Cp, Cy, and Cye POSS moieties.

Block copolymer–nanoparticle composites: Structure, functional properties, and processing

“…Similar increase in the lattice parameter due to NP incorporation was also reported for other systems [151,152]. On the other hand, grafting of various phenyl-functionalized polyhedral oligomeric silsesquioxanes (POSS) on the polybutadiene (PB) block of PS-PB-PS triblock copolymers decreased the lattice parameter by decreasing the degree of SBS block segregation due to favorable interactions between phenyl-POSS and PS that enhance the compatibility between PS and PB blocks [153].…”

Novel elastomer dye-functionalised POSS nanocomposites: Enhanced colourimetric, thermomechanical and thermal properties

“…This can lead to further complications when the objective is to disperse fillers within a particular phase. The incorporation of POSS into SBS has been limited [16][17][18]. Furthermore, SBS-POSS nanocomposites are usually prepared with grafting reactions.…”

Novel elastomer‐dumbbell functionalized POSS composites: Thermomechanical and Morphological Properties

“…Because of the limited volume of polymer available for the phenylPOSS to disperse throughout, at higher filler loadings (10 and 20Áwt %) small fractions of phenylPOSS may be present within the soft, polybutadiene domains, reducing the T g . 36 Composites functionalized with adipoyl chloride displayed higher T g values than those treated with sebacoyl chloride. This was due to the structure of adipoyl chloride's butane chain segment, which allows for additional restraint on molecular motions.…”

“…The incorporation of POSS into SBS has been limited. [36][37][38] Furthermore, SBS-POSS nanocomposites are usually prepared with grafting reactions. This provides the opportunity of preparing these nanocomposites using physical blending techniques and to determine whether adequate filler dispersion can be achieved.…”