The present studies provide the first example of controlled free radical polymerization of a cyclopolymerizing monomer, i.e. diallyldimethylammonium chloride (DADMAC) via reversible addition fragmentation chain transfer (RAFT) chemistry in the presence of trithiocarbonate agent in aqueous solution at 60 °C under microwave irradiation. The polymers [poly(diallyldimethylammonium chloride), PDADMAC] were soluble in water. The structural characterization of the polymers was achieved via NMR spectroscopy. The cyclization reactions during DADMAC polymerization under microwave irradiation attained higher conversions at each time interval as compared to thermal heating. The rate enhancements till around 520% were seen for some reactions. High molecular weight PDADMAC with narrow polydispersities (approaching PDI ≈ 1.05) could be made using microwave irradiation.magnified image

For the first time, controlled/living free-radical polymerization of a cyclopolymerizing monomer, that is diallyldimethylammonium chloride (DADMAC), was achieved via reversible addition fragmentation chain transfer (RAFT) chemistry in the presence of both trithiocarbonate and xanthate RAFT/macromolecular design via the interchange of xanthate (MADIX) agents in aqueous solution at 60, 80, and 90 °C. The structural characterization of the polymers was achieved via nuclear magnetic resonance spectrometry, indicating that during the RAFT polymerization of DADMAC, identical to its equivalent conventional free radical polymerization, five-membered rings are formed almost exclusively. In the case of the trithiocarbonate agent, there was excellent agreement between the theoretical and experimental number average molecular weights, M n, with narrow polydispersities (approaching polydispersity index (PDI) ≈ 1.10) being observed (2100 g mol-1 < M n < 51 000 g mol-1). Chain extension was carried out by sequential batchwise addition of the monomer, confirming the living character of the system. However, the increase in M n with respect to conversion was not linear in the case of the xanthate agent, yet the PDIs were as low as 1.12, indicating that control was achieved. The inclusion of NaCl into the reaction mixture reduces of the rate of polymerization for both RAFT agents. Such an observation supports the hypothesis that electrostatic repulsion is crucial to fragmentation of the primary propagating radicals from the adduct RAFT radical; that is, it appears that an electrostatic interaction is affecting the (chemical) RAFT equilibrium.

This work highlights the formation and use of tenside-free biodegradable polyester dispersions in water for making water stable nanofibers in accordance with the method of “Green Electrospinning”. The concept was to use the amphiphilic block copolyesters poly[(hexamethylene adipate)-block-(methoxypolyethylene glycol)] (PHA-b-MPEG) and poly[(ε-caprolactone)-block-(methoxypolyethylene glycol)] (PCL-b-MPEG) for making tenside-free water dispersions. Different copolymers with varied block lengths were synthesized and converted to high-concentration aqueous dispersions by the solvent displacement method followed by dialysis. The dispersions were electrospun with solid contents of up to 28 wt %. Via addition of small amounts of a high-molecular weight poly(ethylene oxide) as a template polymer, the dispersions were processed to nanofiber nonwovens by electrospinning. Water stable PHA-b-MPEG and PCL-b-MPEG nanofibers were obtained by aqueous extraction of the nanofibers.

Four quaternary ammonium salt monomers (2a–d) were synthesized from N,N‐dimethylaminoethyl methacrylate and subsequently polymerized to afford cationic polymers (3a–d). The synthesized monomers and polymers were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. Molecular weights of the synthesized polymers were determined using gel permeation chromatography. Polymer/clay nanocomposites (4a–d) were prepared using solution‐intercalation method and characterized by FTIR, X‐ray diffraction, high‐resolution transmission electron microscopy, energy dispersive X‐ray, and thermogravimetric analysis. Data analysis showed that polymer/clay nanocomposites have intercalated structure. The dielectric properties of the polymer/clay nanocomposites were studied as a function of both temperature and frequency. POLYM. COMPOS., 37:2950–2959, 2016. © 2015 Society of Plastics Engineers

Poly(N,N‐dimethylaminoethyl methacrylate)/clay nanocomposites (4a–c) were prepared by in‐situ bulk polymerization method. N,N‐Dimethylaminoethyl methacrylate (DMAEMA) was alkylated using hexyl bromide to afford quaternary ammonium salt (2) which was used in the organomodification process of the clay. The organoclay (3) was dispersed in the DMAEMA monomer at concentrations 1, 3, and 5 wt% and bulk polymerization reactions were conducted to prepare nanocomposites (4a–c), respectively. The prepared nanocomposites were characterized by Fourier transform infrared, X‐ray diffraction (XRD), high‐resolution transmission electron microscopy, and thermogravimetric analysis. The XRD results showed that the polymer/clay nanocomposites have an exfoliated structure. Optical, dielectric, and mechanical properties were also investigated. The prepared polymer (PDMAEMA) film showed a transparency of about 88% and it slightly decreased to 80% for PDMAEMA/clay (5 wt%). The films showed indirectly allowed transition and the optical band gap of the films was evaluated. The dielectric properties of polymer and polymer nanocomposites were discussed. POLYM. COMPOS., 39:2603–2610, 2018. © 2016 Society of Plastics Engineers