[CCoE Notice] UPDATED-Cullen College Dissertation Announcement: Kshitij Sharma-ChBE

[Hutchinson, Inez A]

[Dissertation Defense Announcement at the Cullen College of Engineering]



ORDERING OF BLOCK COPOLYMER THIN FILMS WITH ENHANCED DYNAMICS USING SOLVENT PROCESSING AND IONIC LIQUID ADDITIVES



Kshitij Sharma

July 17, 2024; 10:00 AM – 12:00 PM

Location: AERB, Room: 320

Committee Chairs:
Alamgir Karim, PhD

Committee Members:
Jacinta C. Conrad, Ph.D. | Jeremy Palmer, Ph.D. | Devin L Schaffer, Ph.D |

Jack F Douglas, Ph.D

Abstract

       Block copolymers (BCP) self-assemble into a variety of microstructures defined by the entropic and enthalpic interactions between blocks and with the confining surfaces, as well as their annealing/processing environment. The annealing conditions impact the kinetics of assembly as well as the ordered microstructure and can be different between different techniques. While thermal annealing (TA) exposes the material to heat, other methods like solvent vapor annealing (SVA) and direct immersion annealing (DIA) expose the polymer to a swelling solvent in vapor and liquid state, respectively. Typically, solvent based methods have faster kinetics due to extensive plasticization of the BCP. It can be generally expected that adding more complexity to the processing conditions, say, by combining two or more of these annealing techniques or adding a third component to the BCP system, can further alter the thin film's interactions, ordering kinetics, and morphology evolution.

       With this research we explore how process design can control the self-assembly process by using a sequential combination of different annealing methods. We first study a sequential DIA/SVA + TA process where we find synergies between DIA/SVA and TA microstructures leading to rapid ordering into an equilibrium morphology. The reverse process of TA + DIA/SVA exposes the BCP system to highly non-equilibrium conditions that produce surface instabilities leading to large surface area transition morphologies not observed for BCP films before. Interestingly, with sufficient time of annealing for each step in both forward and reverse processes, the system overcomes any transient morphology and displays complete microstructure reversibility.

      We further explore the development of BCP microstructure in the presence of an ionic liquid (IL) additive. ILs can plasticize BCP systems and alter interactions between blocks and with the substrate. We demonstrate a film casting method that uses a mixture of solvents and IL to dissolve the BCP and order the film in the casting process. The method produces tunable microstructures oriented perpendicular to the film surface on unmodified substrates. We further show that changing the solvent mixture for dissolving the polymer leads to different as-cast morphologies which can be annealed thermally or in solvent to develop various other non-equilibrium morphologies.

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