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(a) Principal scheme of a rigid rod main chain polymer with flexible side chains (left) and the resulting layered structure (right) in a film cast from solution. d is the distance of the main chain layers. (b) Rigid-rod-like main chain polymers with NLO-active chromophores directly linked to the rigid main chain subunits.
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A structural concept for nonlinear optical (NLO) polymeric materials optimized for long-term stability of the polar order is presented: rigid-rod-like main chain polymers furnished with long alkyl side chains with a portion of the side chains being replaced by NLO-active chromophores were synthesized. The chromophores are rigidly attached to the m...
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Context 1
... work by Ballauff and co-workers on rigid-rod-like polymers showed that solution cast films of the polymers exhibit an ordered lamellar structure with layers oriented parallel to the film surface. [20][21][22] The general architecture of these materials can be described in terms of closely packed rigid rod polymer main chains separated by layers composed of more or less well packed alkyl or alkoxy side chains (Figure 1a). X-ray diffraction and dynamic mechanical measurements clearly demonstrated that the properties of the layers of stiff chains are considerably different from the properties of the side chain layers. ...
Context 2
... temperature transitions have frequently been attributed to the onset of disordering processes ("melting") in the side chain region, while the layered structure and thus the correlation of the main chains are still maintained. Based on the properties of rigid-rod-like polymers substituted with aliphatic side chains we developed a novel concept where NLO-active chromophores are directly linked to the rigid rod main chain (Figure 1b). We expected the motion of the chromophores to be decoupled from the dynamics of the solubility-mediating side chains. ...
Context 3
... this paper we describe the synthesis and characterization of rigid-rod-like polymers with a typical structure as shown in Figure 1b. The theoretical background of our concept as well as the electrooptical measurements will be presented in a following paper (Heldmann, C., Neher, D., Winkelhahn, H.-J., Wegner, G. Macromolecules, in this issue). ...
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Citations
... The synthetic scheme for the preparation of dyes 7ae7c is shown in Scheme 1. Dimethyl 2-amino-5-nitroterephthalate (5) was prepared by the reported procedure [18] from dimethyl 2aminoterephthalate (1). ...
Three disperse azo dyes were synthesized using diazotized dimethyl 2-amino-5-nitroterephthalate (5) followed by the diazo coupling with different N-substituted aromatic amines. The structures of the dyes were confirmed using FT-IR, 1H NMR, 13C NMR, MS and HRMS spectral analysis. The geometries of the azo and hydrazone tautomeric forms of the dyes were optimized at B3LYP/6-31G(d) level of theory, and their electronic excitation properties were evaluated using density functional theory. The computed absorption spectral data of the azo derivatives are in good agreement with the experiment, thus allowing an assignment of the UV–vis spectra. The dyes displayed a broad absorption maximum in the visible region between 498 and 561 nm. The synthesized azo disperse dyes were applied on polyester and nylon fiber and they show very good light fastness and washing fastness properties.
... The step-by-step bisA C H T U N G T R E N N U N G (benzyne) precursor 7 was synthesized from a commercially available product, aminoterephalic dimethyl ester, in four steps according to the reported procedures. [17] As we had difficulties in establishing a full 13 C NMR spectrum of the precursor 4, light-yellow single crystals suitable for X-ray diffraction analysis were grown from a mixed solution of dichloromethane/methanol (1:1) through slow evaporation. Its structure with atomic labeling and crystal data and structure refinement are shown in Figure 1 and Table 1. ...
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... The use of NLO active monomers seems to be a convenient strategy to produce NLO active main-chain organometallic polymers. In fact, rigid rod-like polymers substituted with flexible side-chains can represent a suitable approach to processable NLO materials [23]. Thus, insertion of alkoxy side chains in the rigid structure of the main chain can ensure solubility and amorphism to the polymers. ...
Four new OH-functionalized orthopalladated complexes bearing an electron-donor and an acceptor group in a trans-like arrangement with respect to the metal have been prepared and characterized. The ligands are Schiff bases, bound as C,N- or N,O-chelating moieties. Four new polyesters were obtained by polycondensation from the monomeric complexes and pentyloxyterephthaloyl chloride. Two “model” complexes, each one related to one monomer, were also synthetized, in order to obtain further and more detailed characterization data, and in particular to perform measurements of μβ.
Porosity control and structural analysis of metal-organic frameworks (MOFs) can be achieved using regioisomeric ligand mixtures. While ortho-dimethoxy-functionalized MOFs yielded highly porous structures and para-dimethoxy-functionalized MOFs displayed almost non-porous properties in their N2 isotherms after evacuation, regioisomeric ligand-mixed MOFs showed variable N2 uptake amount and surface area depending on the ligand-mixing ratio. The quantity of N2 absorbed was tuned between 20 and 300 cm³/g by adjusting the ligand-mixing ratio. Both experimental analysis and computational modeling were performed to understand the porosity differences between ortho- and para-dimethoxy-functionalized MOFs. Detailed structural analysis using X-ray crystallographic data revealed significant differences in the coordination environments of DMOF-[2,3-(OMe)2] and DMOF-[2,5-(OMe)2] (DMOF = dabco MOF, dabco = 1,4-diazabicyclo[2.2.0]octane). The coordination bond between Zn²⁺ and carboxylate in the ortho-functionalized DMOF-[2,3-(OMe)2] was more rigid than that in the para-functionalized DMOF-[2,5-(OMe)2]. Quantum chemical simulation also showed differences in the coordination environments of Zn-SBU (secondary building unit) surrounded by methoxy-functionalized ligands and pillar ligands. In addition, the binding energy differences between Zn²⁺ and regioisomeric ligands (ortho- and para-dimethoxy-functionalized BDCs, BDC = benzene-1,4-dicarboxylate) explained the rigidity and porosity changes of the mixed MOFs upon evacuation, and perfectly matched with experimental N2 adsorption and X-ray crystallography data.
Three new 'hairy' polymers containing 1,3,4-oxadiazole rings in the repeating units have been prepared and investigated by static light scattering. The two polymers of rod-like structure of the main chain show evidence of the same aggregation phenomena as other well known hairy rod polymers. The dimensions of the aggregates increase with increasing the polarity of the solvent. No aggregation occurs in the solution of the third polymer whose spacers, connecting the conjugated segments, are longer. This probably is determined by the increased flexibility of the polymer backbone. The third polymer, though hairy, has no rod-like structure of the main chain. Obviously, the rod-like structure is the determining factor for the aggregation observed. © 2009 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.
In this article we discuss the state of the art in the field of second-order non-linear optical polymers. More specifically, we highlight those results that we think made an important contribution to the field, combined with some of our own results. We start with a general overview of all the aspects involved in characterizing second-order non-linear optical polymers, from thin film formation and poling to second-harmonic generation and electro-optic measurements on such systems. Next, we review the second-order non-linear optical properties of selected polymer systems such as poly(vinyl ether)s, polystyrenes, polymethacrylates, main-chain polymers and high Tg polymers like polyimides and polymaleimides. Finally, we discuss some new polymer systems that might become important in the field of non-linear optics in the near future.
For the first time, two nonlinear optical (NLO) main chain dendronized polymers, MDPG1 and MDPG2, were prepared through the Suzuki coupling reaction, by utilizing low generation dendrimers as the monomers. These polymers inherit the advantages of both main chain polymers (which usually demonstrate good stability of NLO effect) and dendronized polymers (which usually possess large NLO coefficient) simultaneously. For MDPG2, its NLO coefficients d33 value and d33(∞) value are up to 116 and 20 pm/V, respectively, very similar to those of the normal dendronized polymer DPG2. Interestingly, thanks to its main chain structure, the onset temperature for the decay of its d33 value was tested to be 100 oC, 30 oC higher than that of DPG2.
A new series of 12 thermotropic liquid crystalline and photocrosslinkable random copolyesters were synthesized from terephthalic acid, isophthalic acid and 4,4'-oxybis(benzoic acid) with four different arylidene diols and a common diol 1,2-bis(4-hydroxybenzoyloxy)ethane by direct polycondensation with diphenylchlorophosphate. The resulting polymers had inherent viscosities in the range 1.20–1.74 dl/g. Their structural features were investigated by Fourier transform infrared (FTIR), 1H, and 13C nuclear magnetic resonance (NMR) spectroscopy. The thermal behaviour of the copolyesters was investigated with differential scanning calorimetry and hot stage optical polarized microscopy. Our investigation on the effect of monomer structure on liquid crystalline behaviour shows that the copolymers containing bis(benzylidene)cycloalkanone exhibited higher melting and isotropization temperatures and extended liquid crystalline range. All of the copolymers showed some degree of crystallinity as evidenced by wide-angle X-ray diffraction and scanning electron microscopy. The photocrosslinkability of these polymers was established with UV irradiation/UV spectroscopy and scanning electron microscopy.
In this paper, two new series of hyperbranched main-chain polymers, P1-P6, with chromophore moieties as the core were successfully prepared through "A(3)+B-2" approach via simple Sonogashira coupling reaction. By changing the bulky size of comonomers, the structure-property relationship has been investigated according to the concept of "suitable isolation group". The second harmonic generation (SHG) experiments demonstrated that the hyperbranched structure might be very good architecture for the development of NLO materials with high performance. The benzene ring (Bz) could act as suitable isolation groups in these polymers, while the d(33) values of the corresponding polymers P1 and P4, were 152.6 and 86.2 pm/V, respectively, much higher than their linear analog polymers bearing the same chromophore moieties. In addition, these hyperbranched main-chain polymers could combine the large nonlinearities of hyperbranched polymers and high stability of main-chain polymers, providing a new solution to solve the "nonlinearity-stability" trade off existing in the main-chain polymers to some degree. (C) 2011 Elsevier Ltd. All rights reserved.
This paper deals with relations between solvent diffusion and changes in second harmonic generation (SHG) in a side-group polymer with nonlinear optical (NLO) chromophores. The SHG signal of poled polymer thin films was measured as a function of time during the swelling process with methanol. The results indicated that the diffusion process was Fickian. The topographic results obtained by atomic force microscopy, together with the SHG data, also demonstrated the existence of the domain layer formed during poling that gave rise to the principal SHG intensity for this sample. Also, a noncentrosymmetric chromophore ordering was induced by swelling in the absence of a poling electric field. This time-varying SHG signal upon swelling was discussed in terms of dipolar and polar alignments of the side-group NLO chromophores. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3108–3114, 1999
