Zwitterjoniska homo- och blocksampolymer framställda med RAFT-polymerisation och dessas adsorption till cellulosaytor
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Zwitterionic homo- and block copolymers by RAFT polymerization and their adsorption to cellulose surfaces (English)
Thermo-responsive polymers were directly polymerized from the zwitterionic monomer sulfobetaine methacrylate (SBMA). The polymerizations were performed under homogenous aqueous conditions employing the controlled radical polymerization reversible-addition fragmentation chain transfer (RAFT). 4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid (CTP) was employed as RAFT agent in polymerization of homopolymers poly (sulfobetaine methacrylate) (PSBMA) The target molar-mass for the homopolymers extended from 10.0 kDa to 200 kDa. The reactions were carried out in a salt solution (0.50 M NaCl) where the salt operated as screening agents for the attractive charges within the zwitterionic system according to the anti-polyelectrolyte effect, meaning that added salt enhanced the solubility. The phase transition of the polymers was investigated with UV-Vis spectroscopy where an upper critical solution temperature (UCST) was observed for the systems investigated, except for the two smallest polymers possessing targeted molar masses of 10.0 kDa and 25.0 kDa, respectively. The UCSTs for these polymers were probably below the temperature investigated due to the low molar-mass. The UCSTs for the polymers in this study were found to depend on both the molar-mass and the concentration of polymer in the solution investigated.
An end-functionalized biopolymer (BP) ,was employed as a macroRAFT from which SBMA was polymerized. This resulted in a new type of block copolymer: BP-b-PSBMA. The reactions for the block copolymer were carried out under same conditions as for the homopolymers.
Besides the investigation of the UCST for both homopolymers PSBMA and block copolymers PB-b-PSBMA, an investigation regarding the adsorption of selected polymers on cellulose were performed by quartz crystal microbalance with dissipation (QCM-D) measurements. The QCM-D crystals employed were modified which resulted in a negatively charged cellulose model surface. Besides QCM-D measurements, cellulose filter papers composed of uncharged cellulose fibers were also employed in the investigation of adsorption for the selected polymers. FT-IR measurements were performed on the filter papers for detection of carbonyl peaks that could indicate a successful adsorption of the polymers.
Proton nuclear magnetic resonance (1H NMR) analyses were performed to determine the conversion and the kinetics of the polymerizations. The majority of the polymers possessed pseudo-first order kinetics and additionally exhibited low molar-mass dispersity ĐM (ĐM = Mw/Mn). ĐM values were obtained from size exclusion chromatography (SEC) and were a further verification of a successfully controlled radical polymerization. The surface structures of the cellulose model surface after the adsorption were further evaluated by atomic force microscopy (AFM) micrographs taken of the surfaces. The micrographs revealed a significant difference between the virgin cellulose model surfaces in comparison to the surface with adsorbed BP-b-PSBMA200.
Place, publisher, year, edition, pages
2015. , 61 p.
RAFT, zwitterionic monomers, block copolymer, biopolymer
IdentifiersURN: urn:nbn:se:kth:diva-173358OAI: oai:DiVA.org:kth-173358DiVA: diva2:852786