Title page for ETD etd-12032009-232246

Type of Document Dissertation
Author Hardrict, Shauntrece Nicole
Author's Email Address shardric@vt.edu
URN etd-12032009-232246
Title Dendronized Amphiphilic Copolymers Synthesized from Methacrylate Derivatives as Potential Topical Microbicides
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Richard D. Gandour Committee Co-Chair
Turner, S. Richard Committee Co-Chair
James E. McGrath Committee Member
Judy Riffle Committee Member
Richey M. Davis Committee Member
  • topical microbicide
  • ionomer
  • dendronized polymer
  • amphiphile
Date of Defense 2009-11-05
Availability unrestricted
The need for a preventative agent to curtail the rampant spread of HIV, other STDs and mucosal pathogens is urgent. Topical microbicides based on amphiphilic compounds have been identified as an attractive means toward this goal. Novel dendritic methacrylate macromonomers––di-tert-butyl 4-(2-tert-butoxycarbonyl-ethyl)-4-[3-(2-methacryoloxyethyl)ureido]heptandioate (MI) and di-tert-butyl 4-(2-tert-butoxycarbonylethyl)-4-[3-methyl-3-(2-methacryoloxyethyl)ureido]heptanedioate (MIII)––were synthesized, characterized, and subsequently polymerized via conventional free radical polymerization in acetonitrile employing AIBN as an initiator.

Methyl 3-mercaptopropionate (MMP), a chain transfer agent, was employed to target low molecular weight (<10,000 g/mol) polymers. Dendronized homopolymers were prepared from MIII with varying MMP concentrations (0–10 mol%). MALDI-TOF MS characterized the homopolymer prepared with 10 mol% MMP (Mn = 2,481 g/mol).

In the presence of MMP, MIII (5 to 25 mol%) was copolymerized with alkyl (methyl, ethyl, and n-butyl) methacrylates. Copolymer composition correlated well with monomer feed; Mns of 3–10K g/mol were observed.

Ionizable polymers were achieved via acidolysis with trifluoroacetic acid; significant increases in Tg were observed. For the copolymers, the Tgs of the acids increased as the copolymer composition increased in MIII. For the homopolymers, Tgs decreased with increasing MMP concentration.

The solubilities of carboxylic acid functional polymers were studied in 5 w/v % aqueous triethanolamine (aq TEA) at a concentration of 12.5 mg/mL. Clear, homogeneous solutions of the deprotected macromonomer, MIII(OH), homopolymer, PMIII(OH), and MIII(OH)/MMA copolymer series were observed; copolymer solubility decreased as the aliphatic chain length of the alkyl methacrylate increased.

The amphiphilic dendronized polymer series incorporates many features shown beneficial in the pursuit of effective antimicrobial agents: amphiphilicity, multiple anionic functional groups, a polymer backbone, and aqueous solubility. Additionally, biological selectivity (e.g. cytotoxicity) is expected to be tunable through the control of molecular weight, alkyl chain length (n*), copolymer composition, and molecular architecture.

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