Intramolecular charge transfer complexes

Summary Radical copolymerization of N-(2-hydroxyethyl)carbazolyl methacrylate (HECM, M₁) with 2-ethylacryl-(ETNFA) and 2-ethylmethacryl-(ETNFM)-4,5,7-trinitro-9-fluorenon-2-carboxylate (M₂), respectively, can be approximated by the simple terminal model having the parameters : HECM-ETNFM r₁ = 0.66 r₂ = 0.40 HECM-ETNFA r₁ = 0.84 r₂ = 0.10Two intramolecular charge transfer complexes copolymers are obtained. Analysis of intramolecular complexation suggests a more complicated copolymerization mechanism, especially in the case of HECM-ETNFA system. Also, the complexation aeems to be independent on the acrylate or methacrylate type of the comonomers.Dedicated to Prof. G. B. Butler on the occasion of his 65th anniversary     

Radical copolymers of 2-vinyl pyridine with methyl acrylate and methacrylate. A study of microstructures by 1H n.m.r.

Radical copolymerization of 2-vinyl pyridine with methyl acrylate and methacrylate, respectively, has been carried out in benzene solution with low conversion. The reactivity ratios for the two systems, have been determined using the Fineman-Ross and Kelen-Tüdös methods. The values obtained satisfy the terminal model of copolymerization. The signals sensitive to sequence distribution and configuration in the ¹H n.m.r. spectra are αCH₃ and OCH₃ from methyl methacrylate, OCH₃ from methyl acrylate and the aromatic proton signal from 2-vinyl pyridine. The configurational model for the two types of copolymers is discussed using the information from the signals together with influence of the neighbouring and next-neighbour units on signal splitting.     

Photocrosslinked surface relief gratings on azobenzene-containing copolymer films

An amorphous polymer containing Disperse Red 1 (DR1) and crosslinkable acrylic groups as separate side groups was synthesized. Surface relief gratings were optically inscribed onto films of this polymer. Grating depths of 350 nm were obtained after 40 min of irradiation. The first-order diffraction was monitored during the laser irradiation, and an efficiency of about 22% was achieved. The polymer could be photocrosslinked at 80 °C under UV light. Although some photo-degradation due to UV irradiation of the azo chromophores was observed, the surface relief itself was fixed by the photocrosslinking, as observed by the improved thermal stability of the diffraction efficiency. Even after heating above the glass transition temperature (T_g) for 2.0 h, significant diffraction was still present and the grating was still observed. In comparison with the photocrosslinked gratings, a non-crosslinked grating rapidly lost most of its shape when heated above T_g. Thus, photocrosslinking is a useful method to improve the thermal stability of the gratings.     

Intramolecular charge transfer complexes

Summary Radical copolymerization of N-ethyl-3-hydroxymethyl cartbazolyl methacrylate (EHMCM) with methacryloyl--hydroxyethyl-3,5-dinitrobenzoate (DNBM) and acryloyl--hydroxyethyl-3,5-dinitrobenzoate (DNBA), respectively, lead to intramolecular charge transfer complexes (CTC). In the case of EHMCM-DNBA copolymerization, a mechanism involving intermonomeric CTC participation is evidenced.Dedicated to Professor B. Vollmert's 60th anniversary     

Plasma-induced polymerization

Summary High molecular weight methacrylonitrile (M₁) — styrene (M₂) copolymers were obtained by plasma-induced bulk copolymerization. The reactivity ratios, determined by Kelen — Tüdös method, were shown to be r₁=0.21 and r₂=0.34 and indicate a radical mechanism of polymerization. Some microstructural aspects of the obtained copolymers are presented.     

Comparison of intramolecular complexation in several charge transfer complexes copolymers

Summary Another representation of the chemical shift of the acceptor structural units' protons in the NMR spectra is proposed in order to make possible direct comparison between intramolecular complexation in intramolecular charge transfer complexes obtained by copolymerization. The influence of synthesis conditions and comonomer type on the intramolecular complexation is discussed.More experimental data are neededto elucidate these findings.     

Intramolecular charge transfer complexes

Summary A new acceptor monomer (methacryloyl -hydroxyethyl-3,5-dinitrobenzoate), having an increased distance between the acceptor group and the double bond, was copolymerized with N-(2-hydroxyethyl)carbazolyl methacrylate and acrylate, respectively. The copolymers are strong intramolecular charge transfer complexes, even at high temperatures. Because the increased distance between the acceptor group and the main chain permits a favourable steric arrangement of the donor and acceptor groups, the intramolecular complexation is independent on copolymer configuration.     

Intramolecular charge transfer complexes

Summary Radical copolymerization of acryloyl (PtA)- and methacryloyl (PtM)-2-hydroxyethyl-2-(N-phenothiazinyl)propionate with methacryloyl-2-hydroxyethyl-3,5-dinitrobenzoate proceeds through a mechanism which implies intermonomeric complex participation. There are indirect proofs that the intramolecular charge transfer complexes obtained present a total electron transfer phenomenon at high temperatures.     

Intramolecular charge transfer complexes 5

Summary Copolymerization of N-(2-hydroxyethyl) carbazolyl mathacrylate (M₁) with 2,4-dinitrophenyl methacrylate (M₂) takes place through the simple terminal mechanism having the parameters r₁=0.35 and r₂=0.53. Intramolecular charge transfer complexes with different donor/acceptor ratios are obtained. The intramolecular complexation is correlated with the alternating diad fraction and with the copolymer conformation through the ¹H-NMR spectra registration temperature.     

Structure–properties relations of thermally cured epoxy–lignin polyblends

A bisphenol A based epoxy adhesive (EP) was modified by polyblending with Kraft Lignin (L). A systematic investigation of the thermally cured EP-L polyblends with up to 40% by weight L was undertaken. Adhesive shear tests, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid-state CP-MAS NMR spectroscopy were performed to establish the effect of L on the mechanical properties of the polyblends and on the morphology of these crosslinked structures. The possibility of an enhanced degree of bonding between L and the EP network is discussed. This bonding can arise from a chemical reaction between L and some unreacted amine groups present in the hardener.