Improved self-assembly of poly(dimethylsiloxane-b-ethylene oxide) using a hydrogen-bonding additive.
Block copolymers with increased Flory–Huggins interaction parameters (χ) play an essential role in the production of sub-10 nm nanopatterns in the growing field of directed self-assembly for next generation lithographic applications. A library of PDMS-b-PEO block copolymers were synthesized by click chemistry and their interaction parameters (χ) determined. The highest χmeasured in our samples was 0.21 at 150 °C, which resulted in phase-separated domains with periods as small as 7.9 nm, suggesting that PDMS-b-PEO is a prime candidate for sub-10 nm nanopatterning. To suppress PEO crystallization, PDMS-b-PEO was blended with (l)-tartaric acid (LTA) which allows for tuning of the self-assembled morphologies. Additionally, it was observed that the order-disorder transition temperature (TODT) of PDMS-b-PEO increased dramatically as the amount of LTA in the blend increased, allowing for further control over self-assembly. To understand the mechanism of this phenomenon, we present a novel field-based supramolecular model, which describes the formation of copolymer-additive complexes by reversible hydrogen bonding. The mean-field phase separation behavior of the model was calculated using the random phase approximation (RPA). The RPA analysis reproduces behavior consistent with an increase of the effective χ in the PDMS-b-(PEO/LTA suprablock).