Synthesis and Characterisation of Initiators and Amphiphilic Miktoarm Star Polymers

Abstract

This project involves the development of several novel heterofunctional initiators with a calix[4]arene centre that can facilitate a “core” first method for the synthesis of miktoarm star polymers.
Chapter 1 introduces main concepts on calixarenes, single electron transfer living radical polymerisation and the ring opening polymerisation of ε-caprolactone.
Chapter 2 describes the synthetic strategy employed for the synthesis of a novel A2B2 heterofunctional initiator that incorporated an alkyl halogen moiety and a primary hydroxyl. p-tert-butylcalix[4]arene was modified via a six step process to introduce the required functionality and was fully characterised at each stage using 1D and 2D NMR spectroscopy, ASAP MS and IR spectroscopy.
Chapter 3 describes how the A2B2 heterofunctional initiator was used to synthesise a novel 2-armed PCL polymer centred on a calixarene core. This was further used for copper(0) mediated polymerisation of 2-hydroxyethylacrylate due to the alkyl halide moieties remaining in the calixarene core, leading to the formation of several amphiphilic A2B2 miktoarm star polymers. Both polymers were fully characterised using 1D and 2D NMR spectroscopy, SEC, DSC, TGA and IR spectroscopy.
Chapter 4 describes the synthetic strategy employed for the synthesis of a novel A4B4 heterofunctional initiator that incorporated an alkyl halogen moiety and a primary hydroxyl. p-tert-butylcalix[4]arene was modified via a seven step process to introduce the required functionality and was fully characterised at each stage using 1D and 2D NMR spectroscopy, ASAP MS and IR spectroscopy.
Chapter 5 describes how the A4B4 heterofunctional initiator was used to synthesise a novel 4-armed star PCL polymer centred on a calixarene core. This was further used for copper(0) mediated polymerisation of 2-hydroxyethylacrylate due to the alkyl halide moieties remaining in the calixarene core, leading to the formation of several amphiphilic A4B4 miktoarm star polymers. Both polymers were fully characterised using 1D and 2D NMR spectroscopy, SEC, DSC, TGA and IR spectroscopy.
Chapter 6 described the self-assembly of A2B2 and A4B4 amphiphilic miktoarm star polymers calixarene-A2B2starPCL100PHEAm, 8-10, where m = 75, 100 and 270, respectively and calixarene-A4B4starPCL20PHEAm, 18, 19 and 20 where m = 10, 25 and 48, respectively). The TEM analysis on polymer systems 8 - 10 and 18 - 20, revealed spherical micelles, with the size of the micelle decreasing as the proportion of hydrophilic PHEA increased. The CMC determinations for polymers 8 – 10 revealed that the length of the hydrophilic chain does not appear to have a significant effect on the CMC. For polymers 18 – 20, the CMC increases as the length of the hydrophilic polymer chain increases. For both polymeric systems 8 - 10 and 18 - 20, low CMC values were calculated. This work showed the system has a potential in medical applications, with their ability to form micelles in the range of 5 to 110 nm and have the ability to encapsulate highly hydrophobic material, such as the fluorescent probe pyrene.
In chapter 7 general conclusions and future perspectives for the work are discussed.