Renewable Resource Based Block Copolymers and Their Self Assembly

Abstract

The objective of this thesis is to incorporate the bio-resource based vesicular directing group, pentadecyl phenol (PDP), into caprolactone based block copolymers and see its effect onto the self assemblies of these polymers. For this purpose PDP substituted caprolactone monomer was synthesized, it was further ring opened using PEG as an initiator to get amphiphillic block copolymer, PEG-b-PPCLn (PPCL-PDP substituted polycaprolactone). Once the repeating units of monomer in a hydrophobic block (PPCLn), necessary for self assembly are optimized, fluorescent tagged polymers (TPE- PPCLn-CPCLm) were synthesized with TPE (tetraphenyl ethene) as an initiator and CPCL (carboxylic substituted polycaprolactone, discussed in introduction) as a hydrophilic block were synthesized and their self assembly was studied. All monomers and polymers were characterized using 1H NMR, 13C NMR and FT-IR. Thermal stability and semicrystallinity of these polymers was checked using thermogravimetric analysis and Differential Scanning Calorimetry respectively and it is found that all polymers are semicrystalline and thermally stable upto 250 °C. Hydrophobicity of all the polymers was analyzed from Water Contact Angle. It was found that, PEG-b-PPCLn forms micellar self assemblies whereas TPE polymers produce vesicular assemblies of around 200 nm in water. These nano-assemblies were further characterized using DLS and FE-SEM. Drug loading capabilities of these polymers was checked using dialysis method of self assembly. Cell viability assay of drug loaded nano-carriers suggested that they are cytotoxic to the cancer cells and cellular uptake of these nano-assemblies was confirmed by confocal laser scanning microscopy. Photo-physical studies of TPE-PPCLn-CPCLm were performed and it was found that TPE gives aggregation induced emission upon self assembly and these self assemblies also show FRET upon encapsulation of dye such as Rhodamine-B. Cellular uptake studies of these polymers are under progress.