Figure 1. Evolution of phase morphology of mixed P t BA/PS

Nanoscale Self-Assembly of Well-Defined Asymmetric Mixed Homopolymer Brushes Grafted on Silica ParticlesBin Zhao, University of Tennessee Knoxville, DMR 1007986

Mixed homopolymer brushes, composed of two chemically distinct homopolymers randomly or alternately grafted on solid substrates, represent an intriguing class of environmentally responsive materials. To tap into the full potential of these smart materials in applications, it is necessary to understand how the two polymers self-assemble in the brush layer under various conditions.

We have developed a unique strategy to prepare well-defined mixed homopolymer brushes from Y-initiator (Scheme 1) by combining two different living polymerization techniques. Figure 1 shows the evolution of phase morphology of mixed brushes with one polymer molecular weight fixed at 24.5 kDa and another polymer molecular weight increasing from below to above that of the first polymer, demonstrating the rich phase behavior of mixed homopolymer brushes.

Figure 1. Evolution of phase morphology of mixed PtBA/PSbrushes with PtBA molecular weight (MW) of 24.5 kDa and PS MW from 14.8 (A), to 18.7 (B), to 24.9 (C), and 30.4 kDa (D).

Scheme 1. Synthesis of asymmetric mixed brushes.Macromolecules 2010, 43, 5387-5395; 2010, 43, 8209-8217.

Mr. Chunhui Bao, Ms. Debbie Sayers, and Ms. Debbie Fraser are in the laboratory.

Bin Zhao is presenting a talk in the Department of Macromolecular Science at Fudan University, China on July 8, 2011.

EducationTwo graduate students are supported by this grant to pursue their Ph.D. degrees: Jonathan Horton (4th year) and Chunhui Bao (1st year). Xiaoming Jiang graduated with a Ph.D. degree in 2010. One undergraduate, Roger Wright, participated in this project in summer, 2011.

Outreach• Hosted two high school teachers, Ms. Debbie

Sayers and Ms. Debbie Fraser, in our research laboratory for two weeks in the summer of 2011 and worked with them to develop experiments for their chemistry classes (11 experiments were conducted and evaluated).

• Organized a tour to our lab and Department for 7 students from two local high schools, delivered a 50-min lecture on Introductions to Polymers, and presented five polymer laboratory demos.

• Bin Zhao and Lei Zhu visited their collaborators Drs. Ping Tang and Feng Qiu of Fudan Univ., China in July, 2011 and presented seminars.

Nanoscale Self-Assembly of Well-Defined Asymmetric Mixed Homopolymer Brushes Grafted on Silica Particles Bin Zhao, University of Tennessee Knoxville, DMR 1007986