Reversible addition-fragmentation chain transfer (RAFT) polymerizations have been performed on a Chemspeed Accelerator SLT100 automated synthesizer to polymerize N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) at 70 °C. Azobis(isobutyronitrile) (AIBN) was used as source of radicals and 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT agent. A complete screening in composition of P(DMAEMA-stat-PEGMA) copolymers was elaborated from 0% of PEGMA to 100% of PEGMA. All polydispersity indices of the obtained copolymers are comprised between 1.11 and 1.30. The reactivity ratios have been determined by the extended Kelen-Tu ¨do ¨s method (r DMAEMA ) 0.93 and r PEGMA ) 0.66). The behavior of the pH-and temperature-sensitive copolymers was studied in aqueous solution by measuring the lower critical solution temperature (LCST) by UV/vis spectroscopy. The measurements were performed at three different pH values (4, 7, and 10). At pH 7 and pH 10 it has been observed that the LCST is increasing linearly with the wt % PEGMA in the copolymer feed. On the contrary, at pH 4, the hydrophilicity of the P(DMAEMA-stat-PEGMA) copolymers is too high due to the protonation of the DMAEMA units. Thus, no LCST has been detected for most of them. By varying the pH and the composition of the P(DMAEMA-stat-PEGMA) copolymers, the LCST can be easily tuned between 34.7 and 82.0 °C.
The monomers 2-methyl-2-oxazine (MeOZI), 2-ethyl-2-oxazine (EtOZI), and 2-n-propyl-2-oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring-opening polymerization (CROP) under microwave-assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (T(CP)) are lower than for poly(2-oxazoline)s with similar side chains. However, comparison of poly(2-oxazine) and poly(2-oxazoline)s isomers reveals that poly(2-oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable T(CP).
The application of well-defi ned poly(furfuryl glycidyl ether) (PFGE) homopolymers and poly(ethylene oxide)-b -poly(furfuryl glycidyl ether) (PEO-b -PFGE) block copolymers synthesized by living anionic polymerization as self-healing materials is demonstrated. This is achieved by thermo-reversible network formation via (retro) Diels-Alder chemistry between the furan groups in the side-chain of the PFGE segments and a bifunctional maleimide crosslinker within drop-cast polymer fi lms. The process is studied in detail by differential scanning calorimetry (DSC), depth-sensing indentation, and profi lometry. It is shown that such materials are capable of healing complex scratch patterns, also multiple times. Furthermore, microphase separation within PEO-b -PFGE block copolymer fi lms is indicated by small angle X-ray scattering (lamellar morphology with a domain spacing of approximately 19 nm), differential scanning calorimetry, and contact angle measurements.
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