Utilising novel thiol-acrylate click reactions to synthesise controlled branched polymer emulsifiers

• Main Author: Auty, Samuel
• Published: University of Liverpool 2014
• Subjects: 540; QD Chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664366

The formation of multi-functional thiol materials for “click” reactions in synthetic chemistry has been significantly under-represented due to added practices that are typically required when working with sulfur-containing compounds. An efficient and facile approach to approach to introducing multiple masked thiols at the surface of polyester dendritic materials is presented, avoiding these difficulties, by utilising a xanthate protecting group. One-pot xanthate deprotection and thiol-acrylate Michael additions from the xanthate-functional dendrimers (generation zero to two) has been accomplished for the first time, using three different acrylate substrates of varying chemistry. The dendrimers were fully characterised by 1H and 13C NMR, SEC and either electrospray or MALDI-TOF mass spectrometry, depending upon the generation and nature of the end groups. In a similar fashion, this one-pot methodology was extended to prepare twenty different surface functional LDHs via the use of xanthate functional ATRP dendritic macroinitiators (generation one to four) and six different acrylate monomers. Model reactions and kinetics studies showed that the presence of xanthates within the initiator structure did not complicate the ATRP of tBuMA. The LDHs were fully characterised by 1H NMR and SEC. In the final study, employing one-pot xanthate deprotection and thiol-acrylate Michael addition, four dendritic ATRP macroinitiators with hydrophobic and pH responsive peripheral functionalities were prepared. Polymeric surfactants comprised of LDHs and HPDs were synthesised, varying in end group composition using different dendritic macroinitiators, and through the use of mixed initiating system, using a non-dendritic component. O/w emulsions stabilised by surfactants comprised of linear polymers, LDHs, or mixed linear polymers/LDHs architectures showed coalescence over a long term stability study under neutral and acid conditions. In contrast, o/w emulsions stabilised by surfactants comprised of branched polymers, HPDs, or mixed branched polymer/HPDs architectures showed no coalescence over a long term stability study under neutral and acid conditions. Further dilution and thermal studies to probe emulsion systems stabilised via branched surfactant architectures resulted in emulsion breakdown.