Status: Sixth-year graduate student
Advisor: Prof. R.A. Register
Undergraduate Institution: Clarkson University
Block copolymers can exist in a range of states that are dependent on the constituent blocks and the surrounding environment. At sufficiently high temperatures or in dilute solution the blocks can mix freely and the block copolymer exists in a disordered state. Block copolymers can also microphase separate into specific morphologies due to chemical incompatibility between the covalently bonded blocks. My work is focused on synthesizing linear ABC triblock copolymers that exhibit two levels of ordering either through a crystallization event or two disorder-order transitions.
The first of these systems is linear ABC triblock copolymers with a semicrystalline end block. The goal of the work on this polymer is to demonstrate crystallization induced phase separation in triblock copolymers. This type of behavior is commonly seen where crystallization in diblock copolymers results in a lamellar morphology unless confined in a glassy matrix or in a very strongly segregated melt. However, crystallization driving phase separation in a different part of the system has not been reported. Through appropriate choice of blocks and tailoring of composition it may be possible to demonstrate end block, A block, crystallization driving microphase separation between the B and C blocks.
The second linear ABC triblock copolymer system incorporates three amorphous blocks. Through appropriate choice of blocks and tailoring of composition it should be possible to demonstrate two consecutive ordering transitions. The initial transition upon cooling will be used to segregate the A block forming alternating lamellae of the A and (B + C) blocks. The second transition will occur within the (B + C) lamellae to form structures such as spheres and cylinders of C block inside the B matrix. The use of a solidification transition, such as vitrification, of the A block will set the lamellar structure but is not specifically required for forming these types of structures.