# Presentation: 373517

## SUPRAMACROMOLECULES: STRUCTURE/PROPERTY CONTROL VIA SELF-ASSEMBLY WITH WELL-DEFINED MACROMOLECULESHarry W. Gibson, DMR-0097126 

- SUPRAMACROMOLECULES: STRUCTURE/PROPERTY CONTROL VIA SELF-ASSEMBLY WITH WELL-DEFINED MACROMOLECULESHarry W. Gibson, DMR-0097126

-  We *demonstrated* that narrow molecular weight polystyrenes with dibenzo-24-crown-8 and bis(*m-*phenylene)-32-crown-10 host end groups, and dibenzylammonium and paraquat guest end groups self-assemble selectively via pseudorotaxane formation, leading to chain extension and star polymers1,2 and presaging reversible AB block copolymer formation.  However, we found that in combination of two macromolecular speices, association constants were only 12-61% relative to model small molecule analogs, attributable to entropic costs of the backbones.

- (1)	 H. W. Gibson, Z. Ge, F. Huang, J. W.; Jones, H. Lefebvre, M. J. Vergne, D. M. Hercules, *Macromolecules, ***2005**, *38, *2626-2637.
- (2) F. Huang, D. S. Nagvekar, C. S. Slebodnick, H. W, Gibson, *J. Am. Chem. Soc. ***2005**, *127, *484-485.
- (3) F. Huang, K. A. Switek, L. N. Zakharov, F. Fronczek, C. S. Slebodnick, M. Lam, J. A. Golen, W. S. Bryant, P. Mason, M. Ashraf-Khorassani, A. L. Rheingold, H. W. Gibson, *J. Org. Chem. *
*	***2005**, *70, *3231 - 3241.
- (4) H. W. Gibson, H. Wang, C. S. Slebodnick, J. Merola, S. Kassel, F. Huang, L. N. Zakharaov, P. Gantzel, A. L. Rheingold, *Org. Biomol. Chem., s*ubmitted.
- (5) H. W.Gibson, H. Wang, K. Bonrad, J. W. Jones, C. S. Slebodnick, B. Habenicht, P. Lobue, *Org. Biomol.  Chem. ***2005***, 3, *2114-2121.

- As shown in the Figure below in order to form AB block copolymers from end-functionalized macromolecules in the bulk state, high effective association constant are required. For the commonly available pseudorotaxane systems Ka < 1000 M-1. Taking into account the reduction in association constants now expected as a result of the entropic costs of the polymers, there was a need for greatly improved host-guest systems with Ka values in excess of 104 M-1.

-  To increase Ka, based on analyses of  X-ray structures, we *designed, synthesized and characterized*  a series of new hosts that are preorganized and possess additional

## Broader Impacts

**Scholarship**
- 8 undergraduates (4 females) have actively participated in research since 2000
- 3 M. S. degrees awarded (Jason W. Jones, Feihe Huang, Amy Fletcher) under DMR funding
- 2 Ph. D. degrees (Jason W. Jones, Feihe Huang) since 2000 under DMR funding
- 5 postdocs (2 females) involved to various extents since 2000 under DMR funding
- 52 presentations, including 29 invited lectures (at universities, national and international meetings) since 2000 based on DMR funding
- 31 refereed papers and 6 preprints since 2000 based on DMR funding
- 1 US patent based on DMR funding
**Awards**
- Cook Faculty Research Award, VT Chemistry Department, 2001, Harry W. Gibson
- William Preston Award, best Master’s Thesis at Virginia Tech, 2003, Feihe Huang
- DOE Travel Award to Attend the 53rd Annual Meeting of Nobel Laureates, 2003,  Jason W. Jones
- 2 Departmental Graduate Research Excellence Awards: Jason W. Jones (2003), Feihe Huang (2004)
- Alumni Award for Research Excellence, Virginia Tech, 2004, Harry W. Gibson
- Sigma Xi Award for Outstanding PhD Dissertation, 2005, Feihe Huang
- Outstanding Alumni Award, College of Science, Virginia Tech, 2005, William S. Bryant (PhD 1999, supported by DMR-93-20196
- 	and DMR-97-06909)
**Industrial Connection****: **LUNA Innovations, Inc.

- binding sites. Notable examples are provided by the cryptands **1**3** **and **2**,4 which very strongly** **bind paraquat **3, **Ka = 5.0 x 106 M-1 and Ka = 1.0 x 104 M-1, respectively. A very high yield synthesis of the precursor to **2 **and its *trans *isomer was developed.5
-   To diversify the pool of guests for self-assembly we *discovered *that simple pyridinium salts form pseudorotaxanes with a number of crown ethers and cryptands; for example, **4 **forms a complex with **1 **with Ka = 5.0 x 104 M-1.  The advantage of this family of guests is the ease with which the charges can be removed by deprotonation or reduction, ultimately allowing formation of permanent rotaxane-type linkages in uncharged block copolymers.