Synthesis and Characterization of Biomimetic Brush Polymers

DoctorPolymer materials have received immense attention in biocompatible materials, biosensing devices, memory devices and electrochemicals because of their low-cost fabrication, high flexibility, high mechanical strength, and good scalability. In addition, polymer materials can be tailored by changing their chemical structure. That is, their function can be improved by incorporating specific molecules into the polymer backbone or side chain. There has been considerable research into functionalized brush polymers in recent years; in particular, biomimetic brush polymers have become promising materials in the field of biomaterials for biocompatible medical devices, non-biofouling materials, biosensing devices, and drug delivery systems due to the well-controlled nanostructures of nanoscale thin film. In Chapter II, New brush polymer bearing biotin and phosphorylcholine moieties were synthesized: Poly(oxy(11-(biotinyl)undecylthiomethyl)-ethylene-co-oxy(11-phosphoryl-cholineundecylthiomethyl)-ethylene)s (PECH-BTmPCn: m = 0−100 mol% biotin (BT)-containing bristle; n = 100−0 mol% phosphorylcholine (PC)-containing bristle). All polymers exhibited excellent solution processability. They favorably self-assembled into horizontal multi-bilayer structures in thin films with BT- and PC-enriched surfaces that were driven by the lateral ordering of the fully extended upright bristles and partial interdigitation between the BT and PC end groups of the bristles. Both the hydrophilicity and water sorption of the films increased with the PC content. The PECH-BT100 films revealed remarkably distinctive sensitivity, selectivity, and adsorption abilities for avidin against other proteins. Such remarkable performance was further significantly enhanced for the PECH-BTmPCn films in which PC moieties were incorporated into the BT-rich surface; in particular, the PECH-BT75PC25 films demonstrated the highest performance. Overall, the self-assembly brush copolymers of this study were very suitable for use due to their high performance detection, adsorption, and separation of proteins and receptors, including avidin, which can reveal high affinity and selectivity for BT moiety. In Chapter III, New biomimetic brush copolymer bearing cholesterol and phosphorylcholine moieties were synthesized: Poly(oxy(4-(14-cholenoatenonyl)-1,2,3-triazol-1-yl methyl)ethylene-ran-oxy(4-(14-phosphorylcholinenonyl)-1,2,3-triazol-1-yl methyl)ethylene) (PGA-CholmPCn: m = 0−100 mol% cholesterol (Chol) containing bristle; n = 100−0 mol% phosphorylcholine (PC) containing bristle), detecting a pneumolysin monomer as the target molecule that was synthesized by introducing a cholesterol moiety at the brush end. These brush polymers demonstrated excellent solubility in various organic solvents, which indicated excellent solution processability. Synchrotron grazing incidence X-ray scattering (GIXS) measurements, water contact angle tests, swelling analyses, and protein adsorption tests were conducted to investigate the thin film morphologies, hydrophilicity, and protein adsorption properties of all PGA-CholmPCn polymers. They favorably self-assembled into multi-bilayer structures through the lateral stacking of side chains via the secondary interaction of alkyl bristles and functional end groups. Pneumolysin adsorption of the films increased as follows: PGA-PC100 < PGA-Chol25PC75 < PGA-Chol50PC50 < PGA-Chol75PC25 < PGA-Chol100 depending on the portion of the cholesterol bristles. The PGA-Chol100 film with a Chol-enriched surface revealed remarkably distinctive sensitivity, selectivity, and adsorption ability for pneumolysin against other proteins. Surprisingly, PGA-CholmPCn films incorporating PC moieties on Chol-enriched surface revealed the significantly enhanced accessibility of water-based analyte solution and highest selectivity for pneumolysin monomer against other proteins by avoiding undesired adsorption. Overall, the self-assembly brush copolymers of this study have remarkable pneumolysin detection properties with a suitable morphology for use in tailored diagnostic systems and real-time screening devices. In Chapter IV, New series of diblock copolymers and random copolymer bearing phosphorylcholine and alkyl moieties were synthesized: Poly(phosphorylcholine hexylthiopropyl glycidyl ether-block or random-glycidyl dodecylate)s (PGPSHPC10-b-PGDD30), (PGPSHPC20-b-PGDD20), (PGPSHPC30-b-PGDD10), (PGPSHPC10-r-PGDD30), (PGPSHPC20-r-PGDD20), and (PGPSHPC30-r-PGDD10). These linear diblock and random copolymers were synthesized with narrow and controlled molecular weight distribution by anionic ring-opening polymerization of allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE) with a PPA/t-BuP4 catalyst system and subsequent selective post-functionalizations. Moreover, the synthesized brush polymers bearing hydrophilic phosphorylcholine and hydrophobic alkyl formed stable polymeric micelles in aqueous and organic solvents. Using these results, creating desired micelle structures will be easier, and this can be applied to promising studies that use micelles as drug carriers