PhD Oral: Investigations into Branching in Acrylate Polymerization: Advanced Characterization and Kinetics
School of Physical and Chemical Sciences, University of Canterbury, Christchurch, New Zealand under the supervision of Dr Sarah Masters and Associate Professor Greg Russell
Time & Place
Fri, 23 Feb 2018 10:00:00 NZDT in Room 531, Level 5, West Building (formerly Rutherford Building)
All are welcome
Poly (acrylic acid) (PAA) is a hydrophilic polymer with a wide range of applications, e.g. drug delivery, water purification and scale control. On the other hand, poly (2-ethylhexyl acrylate) (P2EHA) is a hydrophobic polymer. Its long side group also results in a lowglass transition temperature. It has applications in waterborne coatings, pressure-sensitive adhesives and nanocomposites. Both polymers have branching that strongly influences properties. Short branches influence physical properties such as melting point and glass transition temperature, whilst long branches affect rheology. For this reason my thesis has investigated branching in PAA and P2EHA synthesized by conventional radical polymerization, both with and without chain transfer agent and at different temperatures and initial monomer concentrations. The average number of branches per monomer unit (i.e. degree of branching) was quantified by 13C NMR spectroscopy, solution-state for PAA and melt-state for P2EHA. The heterogeneity of branching in PAA was measured by capillary electrophoresis in the critical conditions (CE-CC). For PAA, the degree of branching (DB) increases with reaction temperature due to a rise in the frequency of the reactions leading to branches, and it is reduced by the presence of a CTA. The heterogeneity of branching increases with diversity of branching structure.1 Results were slightly different for P2EHA. Electrospray ionization-mass spectrometry analyses revealed the occurrence of β-scission and of termination products, which was not the case for PAA. The DB of P2EHA is also reduced by the presence of a CTA, but its increase with temperature is not observed anymore due to the β-scission becoming important.2 Backbiting rate coefficients of PAA and P2EHA were evaluated from the DB values.1,2 Further characterization of poly(sodium acrylate) by CE-CC was carried out, and the mechanism of separation has been studied in depth.3
1 J.-B. Lena, A.K. Goroncy, J.J. Thevarajah, A.R. Maniego, G.T. Russell, P. Castignolles, M. Gaborieau, Polymer, 114 (2017), 209-220.
2 J.-B. Lena, M. Deschamps, N.F. Sciortino, S.L. Masters, M.A. Squire, G.T. Russell, Macromolecular Chemistry & Physics, accepted (macp.201700579).
3 J.-B. Lena, A.R. Maniego, J.J. Thevarajah, G.T. Russell, S.L. Masters, P. Castignolles, M. Gaborieau, Journal of Chromatography A, in preparation.