Synthesis And Thermodynamics Of Nanoparticles Prepared By Single Chain Collapse Of Siloxane Containing Linear And Hyperbranched Polymers PDF Download

Single chain polymer nanoparticle (SCPN) synthesis from different polymer precursors using benzocyclobutene (BCB) chemistry and intramolecular crosslinking was investigated in this study. Synthesis of highly fluorinated SCPNs from highly fluorinated uni-block copolymer precursor utilizing `pseudo-high dilution continuous addition technique' was investigated. GPC confirmed selective intramolecular crosslinking and TEM images supported formation of sub-20 nm spherical polymer nanoparticles. Amphiphilic SCPNs prepared via step-wise crosslinking of an amphiphilic di-block copolymer chain were investigated for their morphology using 4 different characterization techniques: TEM, AFM, DLS and DOSY-NMR. TEM and AFM images showed presence of discreet SCPNs as loosely crosslinked coils that flatten out when deposited on the surface forming pancake like morphology with ̃ 20 nm sizes. All the techniques showed presence of bimodal size distribution of these nanoparticles in solution. A smaller sized distribution represented discreet SCPNs whereas larger sized (>40 nm) distribution represented physical aggregates of SCPNs. These aggregates were broken down upon significantly diluting the solution of nanoparticles (=50 ng/mL). AFM analysis and water contact angle studies on thin films of amphiphilic SCPNs and polystyrene homopolymer blends proved that nanoparticles possess Janus-type morphology. In order to aid synthesis of SCPNs from block copolymer precursors, a new 2-component room temperature polymer crosslinking based on 1-acetoxyBCB containing polymers and a nucleophile was developed. Development of this system involved developing synthesis of new monomer (1-acetoxy-4 and 5-vinylBCB), synthesis of polymers containing this new monomer followed by optimization of their crosslinking reaction. Mechanism of crosslinking and structure of crosslinking unit formed for this crosslinking system was also identified. SCPNs were synthesized at room temperature from uni-block copolymer precursors using this new crosslinking system. Crosslinking reaction was characterized using 1H NMR, GPC and LS-GPC. Symmetric ABA tri-block copolymer precursors are proposed as precursors for synthesis of SCPNs of different morphologies employing intramolecular crosslinking. Initial results on synthesis of ABA tri-block copolymer containing highly immiscible blocks using chain extension approach is also reported.