Manipulation of Crystallization Sequence in PEO-b-PCL Films Using Solvent Interactions

Abstract

The physical structure of polymer films is important for understanding the observed macroscopic properties. In crystalline−crystalline block copolymers, the hierarchical nature of assembly is even more influential. Controlling this assembly process is crucial for tailoring film properties. In materials where crystallization of each block occurs nearly simultaneously, the ability to manipulate crystallization order is desirable. Poly-(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) films were monitored via ATR-FTIR to determine the crystallization order during drying from varying solvents. PCL crystallized first from most solvents except toluene and ethyl acetate, where PEO nucleation occurred first. Moreover, after melting the sample to remove solvent−polymer interaction effects, PCL was first to crystallize from the melt, as has been previously reported. Differences in the films' morphologies based on crystallization order were observed using polarized optical microscopy. These results demonstrate that the order of crystallization and the assembly within the film were controllable when casting symmetric diblock PEO-b-PCL films from different solvents.

Recent progress in block copolymer crystallization

“…On the other hand, PEO‐ b ‐PCL is the most common example of BCP coincident crystallization with a large collection of research literature . The two studies presented here have expanded the scope to include the influence of solvent quality in film formation and additives for ionic conductivity . Brigham and coworkers manipulated the crystallization sequence of symmetric PEO‐ b ‐PCL copolymer films ( M n overall = 20.3k, w PEO = 0.49) using different casting solvents.…”

“…The two studies presented here have expanded the scope to include the influence of solvent quality in film formation and additives for ionic conductivity . Brigham and coworkers manipulated the crystallization sequence of symmetric PEO‐ b ‐PCL copolymer films ( M n overall = 20.3k, w PEO = 0.49) using different casting solvents. Typically, PCL crystallizes first from the melt and chloroform, the most common solvent for preparation.…”

“…As new chemistries are developed, as well as new analytical techniques, stronger foundations in BCP crystallization are needed to evaluate and predict structure-property relationships. This initial section covers some of the primary work in BCP phase behavior and accompanying crystallization analysis including, but not limited to, rAC (T g < T c ) or gAC (T g > T c ) copolymers, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] CC copolymers, [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] thin films, [25,27,28,46,48,56] confined crystallization, [30][31][32][33][34]…”

“…On the other hand, PEO-b-PCL is the most common example of BCP coincident crystallization with a large collection of research literature. [15,16] The two studies presented here have expanded the scope to include the influence of solvent quality in film formation [52] and additives for ionic conductivity. [53] Brigham and coworkers [52] similar T c s is poly(β-propriolactone) (PPL) and PE (PPL-b-PE), which is strongly segregated in the melt.…”

“…[15,16] The two studies presented here have expanded the scope to include the influence of solvent quality in film formation [52] and additives for ionic conductivity. [53] Brigham and coworkers [52] similar T c s is poly(β-propriolactone) (PPL) and PE (PPL-b-PE), which is strongly segregated in the melt. [54,55] To obtain similar T c s, the PE block had 18 mol% ethyl branches to reduce its T c to one closer to T c PPL .…”