title: Molecular Differentiated Initiator Reactivity in the Synthesis of Poly(caprolactone)-Based Hydrophobic Homopolymer and Amphiphilic Core Corona Star Polymers.
abstract: Macromolecules that possess three-dimensional, branched molecular structures are of great interest because they exhibit significantly differentiated application performance compared to conventional linear (straight chain) polymers. This paper reports the synthesis of 3- and 4-arm star branched polymers via ring opening polymerisation (ROP) utilising multi-functional hydroxyl initiators and Sn(Oct)2 as precatalyst. The structures produced include mono-functional hydrophobic and multi-functional amphiphilic core corona stars. The characteristics of the synthetic process were shown to be principally dependent upon the physical/dielectric properties of the initiators used. ROP's using initiators that were more available to become directly involved with the Sn(Oct)₂ in the "in-situ" formation of the true catalytic species were observed to require shorter reaction times. Use of microwave heating (MWH) in homopolymer star synthesis reduced reaction times compared to conventional heating (CH) equivalents, this was attributed to an increased rate of "in-situ" catalyst formation. However, in amphiphilic core corona star formation, the MWH polymerisations exhibited slower propagation rates than CH equivalents. This was attributed to macro-structuring within the reaction medium, which reduced the potential for reaction. It was concluded that CH experiments were less affected by this macro-structuring because it was disrupted by the thermal currents/gradients caused by the conductive/convective heating mechanisms. These gradients are much reduced/absent with MWH because it selectively heats specific species simultaneously throughout the entire volume of the reaction medium. These partitioning problems were overcome by introducing additional quantities of the species that had been determined to selectively heat.
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. dengeileen@hotmail.com.
authors.forename: Eileen
authors.initials: E
authors.lastname: Deng
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. nguyen.nam@hotmail.co.uk.|School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK. nguyen.nam@hotmail.co.uk.
authors.forename: Nam T
authors.initials: NT
authors.lastname: Nguyen
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. frederichild@gmail.com.|School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK. frederichild@gmail.com.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Hild
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. I.Hamilton@bham.ac.uk.
authors.forename: Ian E
authors.initials: IE
authors.lastname: Hamilton
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. enzgd1@exmail.nottingham.ac.uk.
authors.forename: Georgios
authors.initials: G
authors.lastname: Dimitrakis
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. Sam.Kingman@nottingham.ac.uk.
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Kingman
authors.affiliation: Department of Chemical and Environmental Engineering, University of Nottingham Malaysia Campus, Jalan Broga, Semenyih 43500, Selangor Darul Ehsan, Malaysia. Phei-Li.Lau@nottingham.edu.my.
authors.forename: Phei-Li
authors.initials: PL
authors.lastname: Lau
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. derek.irvine@nottingham.ac.uk.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Irvine
mesh_terms: D060326:Chemistry Techniques, Synthetic; D057927:Hydrophobic and Hydrophilic Interactions; D015394:Molecular Structure; D011091:Polyesters / Q000737:chemistry*; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature
chemical_list: D011091:Polyesters; D011108:Polymers; C016240:polycaprolactone
keywords: core corona star; dielectric properties; microwaves; ring opening polymerisation; star polymer