Synthesis and characterization of new water soluble polymers composed of biocompatible/biodegradable building blocks.

摘要

The synthesis and characterization of water-soluble zwitterionic poly(tyrosine), dendronized analogues of the same polymer, and non-ionic triethylene glycol (TrEG) -based dendritic macromoledules are investigated. Poly(tyrosine) linked through the phenol groups is synthesized under environmentally friendly conditions using tyrosine as the monomer and a polymer modified laccase as the catalyst. The chemoselectivity of enzyme used produces a unique unatural poly(amino acid) with phenylene and/or oxyphenylene linked backbone and free amino acid side groups. The amino-acid containing poly(tyrosine) has molecular mass Mw up to ∼82, 000 Da and displays reversible pH-responsive solution behavior. An isoelectric point (IEP) at pH 2.6 has been determined via measurement of zeta-potential. Chain conformation dependence on external pH due to intramolecular electrostatic interactions is manifested by the increase of hydrodynamic diameter Dh from 2.4 nm at IEP to 6.7 nm at pH 1.2 and 10 nm at pH 11.8.;In order to multiply the functionality of linear poly(tyrosine), hydrophilic dendrons are covalently attached onto the backbone to generate a new array of dendronized polymers. For this purpose hydrophilic dendrons and dendrimers are prepared divergently via a "click" reaction approach from hydrophilic and biocompatible building blocks: TrEG and bis-methylolpropionic acid (bis-MPA). Dendrimers up to third generation with precise structure have been successfully produced and characterized by NMR, MALDI-TOF, SEC, and DLS. The new poly(ether-ester) dendrimers up to Mn 15, 800 Da (G3) bearing two triazol rings at each branch site can also serve as a derndritic ligands for palladium (II) complexation. The catalytic capabilities of the complexes are confirmed by carrying out Suzuki-Miyaura reactions in aqueous media.;The modification of poly(tyrosine) into multi-functional dendronized polymer has been achieved through enzymatic polymerization of pre-formed macromonomers under environmentally benign conditions (45°C, in water). The dedronized polymers consisting of poly(tyrosine) backbone and TrEG based dendrons self-assembled in water to form aggregates with generation dependant morphologies.