Iodine-Transfer Polymerization (ITP) of Ethylene and Copolymerization with Vinyl Acetate

Controlled radical polymerization of ethylene using different commercially available, cheap, and non-toxic iodo alkyls is performed by iodine transfer polymerization (ITP) under mild conditions (≤100 °C and ≤200 bar). The formed well-defined iodo end-capped polyethylene (PE-I) species is very stable upon storage. Narrow molar-mass distributions (dispersities around 1.6) were obtained up to number average molar masses of 7300 g mol^-1 . The ethylene copolymerization by ITP (ITcoP) with vinyl acetate allowed to form a broad range of poly(ethylene-co-vinyl acetate) (EVA) containing from 0 to 85 mol % of VAc unit. In addition, EVA-b-PE block copolymers or EVA-b-EVA gradient block copolymers with different content of VAc in the blocks were obtained for the first time using ITP. Finally, reactivity trends were explored by a theoretical mechanistic study. This highly versatile synthetic platform provides a straightforward access to a diverse range of well-defined PE based polymer materials.

Tailoring adhesion of anionic surfaces using cationic PISA-latexes - towards tough nanocellulose materials in the wet state

Cationic latexes with Tgs ranging between -40 °C and 120 °C were synthesised using n-butyl acrylate (BA) and/or methyl methacrylate (MMA) as the core polymers. Reversible addition-fragmentation chain transfer (RAFT) combined with polymerisation-induced self-assembly (PISA) allowed for in situ chain-extension of a cationic macromolecular RAFT agent (macroRAFT) of poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA), used as stabiliser in so-called surfactant-free emulsion polymerisation. The resulting narrowly distributed nanosized latexes adsorbed readily onto silica surfaces and to model surfaces of cellulose nanofibrils, as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. Adsorption to anionic surfaces increased when increasing ionic strength to 10 mM, indicating the influence of the polyelectrolyte effect exerted by the corona. The polyelectrolyte corona affected the interactions in the wet state, the stability of the latex and re-dispersibility after drying. The QCM-D measurements showed that a lower Tg of the core results in a more strongly interacting adsorbed layer at the solid-liquid interface, despite a comparable adsorbed mass, indicating structural differences of the investigated latexes in the wet state. The two latexes with Tg below room temperature (i.e. PBATg-40 and P(BA-co-MMA)Tg3) exhibited film formation in the wet state, as shown by AFM colloidal probe measurements. It was observed that P(BA-co-MMA)Tg3 latex resulted in the largest pull-off force, above 200 m Nm-1 after 120 s in contact. The strongest wet adhesion was achieved with PDMAPMA-stabilized latexes soft enough to allow for interparticle diffusion of polymer chains, and stiff enough to create a strong adhesive joint. Fundamental understanding of interfacial properties of latexes and cellulose enables controlled and predictive strategies to produce strong and tough materials with high nanocellulose content, both in the wet and dry state.

Soft and rigid core latex nanoparticles prepared by RAFT-mediated surfactant-free emulsion polymerization for cellulose modification – a comparative study

Latex nanoparticles of high and low T_g-core block-copolymers were produced and their adsorption to (nano)cellulose surfaces was investigated.

Synthesis of poly(N-acryloylmorpholine) macromonomers using RAFT and their copolymerization with methacrylic acid for the design of graft copolymer additives for concrete

Methacrylate end-capped poly(N-acryloylmorpholine) macromonomers (PNAM-MA) of number-average molar mass of about 2400 g mol⁻¹ have been synthesized by post-modification of PNAM chains obtained by RAFT.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance analyses of end-functionalized saccharidic polymers: an example of a useful analytical technique combination

The living cationic polymerization of a saccharidic monomer (1,2:3,4-di-O-isopropylidene-6-O-(2-vinyloxyethyl)-D-galactopyranose, GVE) gives rise to aldehyde end-capped polymers (PGVE--CHO) of low molar masses (<10 000 Da) and low molar mass distribution (<1.2). These polymers were derivatized by selective introduction of either hexamethylenediamine (PGVE-NH2) or 9-fluorenylmethyl carbazate (PGVE-Fmoc) end groups. The resulting polymers were fully characterized by complementary use of nuclear magnetic resonance (1H NMR) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The expected structure according to the polymerization mechanism, the occurrence of side reactions and the success of the post-functionalization reactions were confirmed.