Main-chain Poly Research Articles

The effect of conformational dependent properties of radical cations on poly( N,N ‐dimethylaniline)

The properties of radical cation of poly(N,N-dimethylaniline) were investigated by electrochemical analysis, ESR, and UV-visible spectroscopy. Through quantum-chemical calculations of model molecules using ab-initio methods, we studied the conformation of the side group and main chain of poly(N,N-dimethylaniline). The obtained results showed that the strong absorption of this polymer at 587 nm was a charge transfer band based on the formation of a radical cation. The environmental factors such as temperature and viscosity of the medium exhibit significant effects on the conformation of the main chain and side chain of the polymer, which greatly influences the stability of the radical cation.

Micro-focus X-ray scanning on layers of smectic superstructures

The investigated main chain poly(ester imide)s (PEI) form smectic layers with different superstructures due to a nanophase separation of the rigid mesogens and flexible spacers, which give rise to X-ray reflections in the small angle region (2θ =1-6°; d=2-8 nm). The novel micro-focus X-ray scanning technique at the beamline ID13 (ESRF, France) enables a visualisation of the local orientation of smectic layers in different morphologies such as bâtonnets and spherulites. Previous investigations of the spherulites formed from PEI by optical and electron microscopy, and SAXS indicated a negative birefringence and a lamellar internal structure. The particular feature of these spherulites is their internal smectic layer structure. The present X-ray scanning experiments reveal a radial arrangement of the smectic layers within the spherulite. Furthermore, the micro-beam scanning experiments provide maps of the molecular orientation in different smectic LC-textures. The internal SC-order of a single bâtonnet (10 * 90 µm) could be examined.

Chain extension and biodegradation of poly(butylene succinate) with maleic acid units

Unsaturated groups were introduced into the main chains of poly(butylene succinate) (PBS) by the condensation polymerization of 1,4-butanediol with succinic acid and maleic acid (MA). The resulting aliphatic polyesters were subjected to chain extension via the unsaturated groups with benzoyl peroxide (BPO), BPO/ethylene glycol dimethacrylate (DF), or BPO/triallyl cyanurate (TF). During the condensation polymerization, some of the cis-structured maleate was isomerized into the trans-structured fumarate. The trans-structured fumarate participated in the chain-extension reaction with BPO more than the cis-structured maleate. However, the trans/cis ratio remained practically unchanged when bridging molecules such as DF and TF were used along with BPO. Chain extension of PBS containing 5.7 mol % MA units (PBSM57) resulted in gel formation. Chain extension with BPO/TF made more gels in PBSM57 than chain extension with the other crosslinking agents. Chain extension increased the glass-transition temperature, decreased the melting temperature and crystallinity, and improved mechanical properties such as elongation and tensile strength. The results of the modified Sturm tests showed that the biodegradability of the unsaturated aliphatic polyesters decreased greatly because of the chain extension. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2240–2246, 2000

Main-Chain and Pendant Poly([2]catenane)s Incorporating Complementary π-Electron-Rich and -Deficient Components

A main-chain poly([2]catenane), incorporating an average of 25 repeating [2]catenane units and having an Mn value of 35 kg mol−1, was synthesized by the polyesterification of a [2]catenane monomer composed of a bipyridinium-based tetracationic cyclophane mechanically interlocked with a 1,5-dioxynaphthalene-based macrocyclic polyether. Similarly, two main-chain poly(bis[2]catenane)s, both incorporating an average of 15 repeating bis[2]catenane units and both having Mn values of 45 kg mol−1, were prepared by the copolymerizations of a bis[2]catenane monomer, possessing two hydroxymethyl functions with an appropriate bis(isocyanate). The same copolymerization was employed in order to produce a pendant poly([2]catenane), incorporating an average of 20 repeating [2]catenane units and having an Mn value of 27 kg mol−1, from a [2]catenane monomer possessing two hydroxymethyl groups on its macrocyclic polyether component.

Preliminary communication - The synthesis and thermotropic liquid crystalline behaviour of novel main chain poly(aryl ether ketone)s containing a lateral phenyl group

Novel main chain poly(aryl ether ketone)s containing a lateral phenyl group were synthesized by nucleophilic substitution reactions of 4,4-biphenol and phenylhydroquinone with either 4,4-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 50 and 70 mol% biphenol. Melting (Tm) and isotropization (Ti) transitions both appeared on the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline nematic state. As expected, each of the copolymers had a relatively lower melting transition than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer phenylhydroquinone.

Computer Simulation of Rotator Phases in Liquid-Crystalline Polymers

The high temperature behaviour of the main-chain liquid-crystal polymer poly(hydroxy-benzoic acid) (PHBA) is examined through the use of computer models. PHBA is known to undergo a first order phase transition, at 340°C, from two co-existing orthorhombic crystalline phases to a single pseudohexagonal rotator phase. Although several attempts have been made to establish the nature of this rotator phase, its structure is, as yet, poorly understood. Monte Carlo simulations have been performed on idealised rotator phase models, using energy terms and cell parameters derived from PHBA. Electron diffraction patterns have been simulated, allowing the phase behaviour to be followed. A loss of angular correlations between adjacent molecules is found, which coincides with the crystal-rotator phase transition. The simulated rotator phase structure is compared with previous models which were derived from diffraction data on the basis of symmetry arguments. A possible explanation is proposed for the continued existance of two orthorhombic phases on cooling from the rotator phase.

Influence of the molecular structure on the dynamics in poly(ester-imide)s

Dielectric spectroscopy in the frequency range from 0.1 to 105 Hz was employed to study the molecular dynamics of main-chain poly(ester-imide)s (PEIMs) with varying spacer lengths from 5 to 12 methylene units. For all samples three relaxation processes were observed. The β-process shows an Arrhenius-like temperature dependence with activation energies between 50 and 55 kJ/mol. This process is assigned to a local libration of the ester groups. The α*-process shows a WFL-like temperature dependence. It is assigned to a main-chain-coupled motion of the mesogens around their short molecular axes. The α-process also follows a WFL-like temperature dependence. It is assigned to cooperative main-chain motion of PEIM and it is correlated to the glass transition.

Spectral Analysis of Eight Polymers in SIMS by MO Calculation. Prediction of Cleavage of Polymers and Structural Formula of the Positive-Ion Fragment

Spectra of eight polymers [(CH2-CHR)n (R=H, OH, F, Cl, OCH3, and CONH2), (CF2-CF2)n] and (CH2-CHCN)n in time-of-flight (TOF)- and static(S)-secondary ion mass spectrometry (SIMS), respectively, were analyzed by semiempirical and ab initio molecular orbital (MO) calculations. We predicted where the cleavage of the polymers occurs on sputtering, due to two-center bond energies of the model pentamers by a semiempirical MO calculations using AM1 program; a) the cleavage can occur in any bonds (polyethylene, poly(vinyl methyl ether), polyacrylonitrile), b) the cleavage of the main chain occurs in any bonds, after side chain groups cleaved first (poly(vinyl chloride, poly(acrylamide)), c) the main chain carbons with the side chain group cleave at any bonds of the main chain (poly(vinyl fluoride, poly(tetrafluoroethylene), poly(vinyl alcohol)). We also determined the possible structural formulas of the secondary positive-ion fragments in the range of 0–100 amu by ab initio MO calculations using the HONDO7 program.

Preparation of polymeric alcohol bearing oligo(oxyethylene) moiety by radical polyaddition through ketyl radical

Hydrophilic polymers having both oligo(oxyethylene) moieties and tertiary alcohol units in the main chain were prepared by the radical polyaddition of the dike-tones with distyryl compounds by using samarium(II) iodide as an electron transfer agent. Polyaddition of 4,4′-(1,4-phenylene)bis-2-butanone or 6,9-dioxatetradeca-2,13-dione with distyryl compounds such as 1,15-di(4-ethenylphenyl)-2,5,8,11,14-pentaoxapentadecane, 1,18-di(4-ethenylphenyl)-2,5,8,11,14,17-hexaoxaoctadecane, or 1,21-di(4-ethenylphenyl)-2,5,8,11,14,17,20-heptaoxaheneicosane resulted in the formation of the corresponding polymeric alcohols in moderate yields (46–75%). The produced polymers showed high solubility in common solvents, and their molecular weights estimated by GPC (THF, polystyrene standard) were 5200–8100. No serious difference in the molecular weight of the polymer between after and before the treatment with cerium ammonium nitrate indicated that the produced polymers were inert under the oxidative condition where oxidative cleavage of the main chain of poly(vinyl alcohol) takes place. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 715–720, 1997

Structure of poly( l-glutamate) with n-fluoroalkyl side chains in the solid state as studied by high-resolution 13C NMR spectroscopy

13C CP/MAS and PST/MAS NMR experiments are carried out on poly( l-glutamate) with n-fluoroalkyl side chains over a range of temperatures from 30 to 100°C to elucidate structural features in the solid state in addition to the experimental findings on poly(γ- n-alkyl l-glutamate) reported previously. From these experimental results it was found that the conformation of the main chain depends on the carbon number of the n-fluoroalkyl side chains. The main chain of poly(γ-trifluoroethyl l-glutamate) with short n-fluoroalkyl side chains takes the helix form and that of poly(γ- n-2-(perfluorodecyl)ethyl l-glutamate) with long n-alkyl side chains takes the β-sheet form. These conformational behaviors of poly(L-glutamate) with n-fluoroalkyl side-chains in the solid state are different from those of poly(γ-n-alkyl L-glutamate).

Structure of poly( l-glutamate) with n-fluoroalkyl side chains in the solid state as studied by high-resolution 13C NMR spectroscopy

13C CP/MAS and PST/MAS NMR experiments are carried out on poly( l-glutamate) with n-fluoroalkyl side chains over a range of temperatures from 30 to 100°C to elucidate structural features in the solid state in addition to the experimental findings on poly(γ-n- alkyl l-glutamate ) reported previously. From these experimental results it was found that the conformation of the main chain depends on the carbon number of the n-fluoroalkyl side chains. The main chain of poly(γ-trifluoroethyl l-glutamate) with short n-fluoroalkyl side chains takes the helix form and that of poly(γ-n-2-( perfluorodecyl) ethyl l-glutamate ) with long n-alkyl side chains takes the β-sheet form. These conformational behaviors of poly( l-glutamate) with n-fluoroalkyl side-chains in the solid state are different from those of poly(γ-n- alkyl l-glutamate ) .

Fluorescence and Singlet Energy Migration in Conformationally Restrained Acrylate Polymers Bearing Pendant Chromophores

Fluorescence and singlet energy migration can be studied in chromophore-appended polyacrylates in which conformationally restricted ring structures in the polymer backbone prevent excimer formation. Specifically, two substituted α-methylene-γ-butyrolactones (1a bearing a naphthyl group and 1b bearing a phenanthryl group) and a naphthyl-substituted diethyl 2,6-dimethyleneheptanedioate (2) yield linear polymers with five-membered rings fixed perpendicular to the main chain (poly(1)) or cyclopolymers with six-membered rings in the main chain (poly(2)) upon radical or group transfer polymerization. 4-Methyl-4-(2-naphthyl)butyrolactone (3a), 4-methyl-4-(3-phenanthryl)butyrolactone (3b), and 1-(1-naphthylmethoxycarbonyl)-1-(ethoxycarbonyl)cyclohexane (4) were prepared as spectroscopic models for these polymers. No evidence for excimer emission could be seen in poly(1a) or poly(1b), but poly(2) exhibited weak excimer emission. Defects in the polymer structure of poly(2) correlate with observed sites for excimer formation. Steady-state fluorescence quenching experiments by CCl 4 demonstrate that singlet energy migration occurs intramolecularly along these polymer chains.

Influence of flexible oligo(tetrafluoroethene) segments on the glass temperature of poly(aramide)s and poly(amide imide)s

The insertion of oligo(tetraflouroethene) segments into the main chain of poly(aramide)s and poly(amide imimide)s is accompanied by a decrease of the glass temperature. The decrease is strictly related to the number of CF2-units and is the same for both poly(aramide)s and poly(amide imide)s. The absolute glass temperature depends, however, on the initial structures of the monomeric units. As a consequence ‘mastercurves’ can be constructed by shifting the individual Tg vs. number of CF2-units curves along the temperature axis. A detailed analysis of the data indicates that besides the Tg-mass/‘flexible’ bond of monomeric unit criterion additional volume and interaction dependant packing effects have to be considered for an accurate prediction of the glass temperatures of polymers.

Stereocontrol mechanism of an organozinc complex having chair‐type structure in the polymerization of tert‐butylethylene oxide; comparison with propylene oxide

AbstractA ring‐opening polymerization of racemic tert‐butylethylene oxide (t‐BEO) was carried out with a well‐defined organozinc complex, [CH3OCH2CH(CH3)OZnOCH(CH3)CH2OCH3]2·[C2H5ZnOCH(CH3)CH2OCH3]2 ([Zn‐MP]2,2), as initiator. The 13C NMR analysis showed that the main chain of poly(t‐BEO) is isotactic although the initiation reaction between t‐BEO and [Zn‐MP]2,2 is much less enantioselective compared with the very high selectivity in the propagation stage. In the R,S‐copolymerization reaction of t‐BEO (R/S = 64/36), no change in the optical purity of the residual monomer was observed at any extent of conversion. It was concluded from these results that the enantioselection in the propagation stage at any particular site is perfectly governed by the chirality of the first t‐BEO molecule that entered and reacted at the site of [Zn‐MP]2,2. The mechanism of the stereocontrol processes for the [Zn‐MP]2,2 initiated polymerization of t‐BEO is discussed in comparison with that for the polymerization of propylene oxide.

X-ray analysis of the structure of a thermotropic main-chain liquid-crystalline copolyester

The structure and phase behaviour of the thermotropic main-chain liquid-crystalline copolyester poly[(phenyl-p-phenylene)-co-(terephthalate)-co-(p-hydroxybenzoate)] (PES) prepared from terephthalic acid, phenylhydroquinon andp-hydrobenzoic acid (molar ration 45/45/10) is determined by X-ray diffraction and differential scanning calorimetry. This random copolyester shows up to 340°C periodicc-axis order in its X-ray diffraction pattern as well as sharp and diffuse reflections at the equator and other crystallographic directions, indicating well ordered three-dimensional crystalline structure. Two crystalline modifications are observed for quenched and annealed fibres, which are both orthorhombic with slightly different unit cell sizes. Indications of other phases at still higher temperatures are reported. They are believed to be a novel mesophase followed by a nematic liquid-crystalline phase and the isotropic melt.

Polyarylenes and poly(arylenevinylene)s Part 10. Reductive polycondensation of a sterically hindered monomer

The synthesis of main-chain bromo-substituted poly(1,4-phenylene-diphenylvinylene)s is possible using 1,4-bis(4-tert,butyl-α,α-dichlorobenzyl)benzene as starting material in a reductive dehalogenation polycondensation with chromium(II) acetate as reducing agent. Some difficulties occur during the coupling reaction, connected with the very low solubility of the starting compound and the formation of substituted benzoquinonebismethides as by-products.

An X-Ray Investigation of Thermotropic Polymalonates Containing the Azobenzene Mesogen

Abstract The structure of three main chain poly (α, ω-alkylene) monoalkylmalonate]s containing the azobenzene mesogen was investigated by X-ray diffraction. The mesogenic properties of the samples are compared with those of related side chain or combined polymeric systems

1H n.m.r. study of [formula omitted

The aspartic acid residue can be linked in the main chain of poly(α,β-[N(2- hydroxyethyl)- d,l-aspartamide ]) by its α- or β-carboxyl, forming thus α- or β-structural units. The n.m.r. spectrum of the polymer was assigned by means of two-dimensional correlated spectroscopy. Selective decoupling of some lines in the one-dimensional spectrum showed that the splitting of one of the aliphatic peaks as well as that of the amide peaks is due to the presence of the α- and β-structure. The assignment of this splitting was achieved by means of two-dimensional nuclear Overhauser enhancement spectroscopy. The number of α- and β-structural units was estimated from the spectra with decoupled resonances of one of the CH 2 protons in the side chain. The results show that the α- and β-structure depends on the methods of preparation of the polymer.

The Twist Viscosity Coefficient of A Main-Chain Nematic Polymer: Temperature and Molecular Mass Dependences

Abstract Measurements of the twist viscosity coefficient of the main-chain nematic polymer poly (4,4′ dioxy 2,2′ dimethyl azoxybenzene nonanediyl) are reported. Temperature and mass dependences are studied in detail and analyzed in terms of existing theories. This viscosity scales as the square of the order parameter. The temperature dependence is found to be the same, for different molecular masses. The process is either purely activated or free volume controlled with a rather low “freezing” temperature of the director. For the mass dependence, a power law is observed. The mean value (∼ 4–5) of the exponent suggests a behaviour intermediate between those of rod-like and entangled flexible polymers. Two regimes with different exponents can however not be excluded.

Introduction of carbonyl group to the main chain of poly(phenyl vinyl sulfide)

Introduction of carbonyl group to the main chain of poly(phenyl vinyl sulfide)