Shujun Chen

Postdoctoral Associate
Ph.D. in Polymer Science and Engineering, University of Massachusetts - Amherst (2006)

Self-assembly of New Comb-Rod Dendritic Block Copolymers and Their Co-assembly with Lipids for Tailored Functional Materials

Linear-dendritic hybrid copolymers have attracted much attention in the past decade, as these non-symmetrical copolymers combine the multi-functionality of dendrimers and the phase segregated morphological behavior of traditional block copolymers.   In particular, amphiphilic linear-dendritic block copolymers can self-assemble into stable micellar and vesicular structures, which can be used as targeted drug and gene delivery vehicles.

My project investigates the fundamental nature of solution self-assembly and lipid co-assembly of a family of novel comb-rod dendritic copolymers, which consists of a monodisperse alkyl-modified peptide block with a rod-like helical conformation, poly(N-alkyl-L-glutamate) or PALG, and a biodegradable polyester dendron block, as seen in Figure 1.

Figure 1. Materials Studio® simulated structure of a comb-rod dendritic copolymer with PEG-functionalized dendron termini.1

Previous studies in the Hammond group found that these comb-rod dendritic copolymers self assemble into stable miceller1 or vesicular2 structures, depending on the relative size of the hydrophilic head group.  The vesicle-forming linear-dendritic block copolymers have great promise in their co-assembly with lipids to form unique biomimetic systems that may have interesting transmembrane properties for the transport of ions or small hydrophilic molecules, through the incorporation of unique tunable defects (hydrophilic dendritic headgroups) within the membrane structure.  I will be synthesizing a series of peptide-based comb-rod dendritic block copolymers by systematically varying the alkyl side chain length, dendron generation, and endgroup functionalization.   The solution assembly of such systems as a function of polymer composition as well as their co-assembly with lipid bilayers will be studied, utilizing tools such as dynamic and static light scattering, cryo-TEM, and WAXD/SAXS.

 References: 

  1. Tian L, Hammond PT, “Comb-dendritic block copolymers as tree-shaped macromolecule amphiphiles for nanoparticle self-assmbly”, Chemistry of Materials, 18, 3976-3984 (2006).
  2. Tian L, Nguyen P, Hammond PT, “Vesicular self-assembly of comb-dendritic block copolymers”, Chem. Commun. 33, 3489-3491 (2006).