P. Kannan

CO-ORDINATION POLYMERS

Abstract This paper is a review of the metal complex forming coordination polymers. A polymer–metal complex is composed of synthetic polymer and metal ions bound to the polymer ligand by a coordinate bond. A polymer ligand contains anchoring sites like nitrogen, oxygen or sulphur obtained either by the polymerization of monomer possessing the coordinating site or by a chemical reaction between a polymer and a low molecular weight compound having the coordinating ability. The polymer–metal complexes may be classified into different groups according to the position occupied by the metal, which is decided by the method of preparation. The method include the complexation of polymeric ligand with various metal ions, cross-linked polymers with pendent, ligands forming either intramolecular and/or intermolecular chelating functions are highlighted in the first part. The various works on the coordination complexes has revealed that the heterogeneous systems possess more economical potentials and advantages over homogeneous systems. The co-ordination polymers belong to the former case. The high molecular weight polymer–metal complexes work as storage houses for solar energy. Efficient chemical conversion in the storage of solar energy will be difficult with the homogeneous systems. The synthesis results in an organic polymer with inorganic functions. The metal atoms attached to the polymer backbone are bound to exhibit characteristic catalytic behaviour, which are distinctly different from their low molecular weight analogue. Many synthetic polymer–metal complexes, found to possess high catalytic efficiency, in addition to ion selectivity in waste water treatment, recovery of trace metal ions, and hydrometallurgy are enlightened in the final part.

Synthesis and characterization of a new metal chelating polymer and derived Ni(II) and Cu(II) polymer complexes

Abstract 2-Hydroxy-4-acryloyloxybenzaldehyde (2H4ABA) prepared from acryloyl chloride and 2,4-dihydroxybenzaldehyde, was polymerized in 2-butanone at 65°C using benzoyl peroxide as initiator. Polychelates were obtained in N , N -dimethylformamide solution of poly(2H4ABA) with aqueous solution of Cu(II)/Ni(II) ions. The polymers and polychelates were characterized by elemental analysis and spectral studies. The infra-red spectral data of polychelates suggest that the metals are coordinated through the oxygen of the aldehyde group and oxygen of the phenolic-OH group. The electronic spectra, e.p.r. and magnetic moments of polychelates show an octahedral and square planar structure for poly(2H4ABA) Ni(II) and poly(2H4ABA) Cu(II) complexes respectively. X-ray diffraction studies revealed the highly crystalline nature of polychelates. The thermal properties of polymer-metal complexes and their catalytic activity are discussed.

Novel flame retardant polyphosphoramide esters

Abstract Several new polyphosphoramide esters have been synthesized by solution polycondensation of N,N′-bis(p-chloroformylphenyl)N″-phenyl phosphoric triamide with various aromatic diols. The polymers were characterized by i.r., 1H, 13C and 31P n.m.r. spectroscopy and by their inherent viscosity. Thermo-oxidative stability and flammability of the polymers were evaluated by thermogravimetry and limiting oxygen index values respectively.

Studies on poly(2-Hydroxy-4-methacryloyloxybenzophe-none)-metal complexes

Abstract 2-Hydroxy-4-methacryloyloxybenzophenone (2H4MBP) was prepared and polymerized in 2-butanone at 70 °C using benzoyl peroxide as initiator. Poly(2H4MBP) was characterized by infra-red and 1H-nuclear magnetic resonance spectroscopic techniques. The molecular weight of the polymer was determined by gel permeation chromatography. Cu(II) and Ni(II) complexes of poly(2H4MBP) were prepared. Elemental analysis of polychelates suggests that the metal-ligand ratio is about 1:2. The polychelates were further characterized by infra-red spectra, X-ray diffraction, spectral studies, magnetic moments and electrical conductivity measurements. Thermal analyses of the polymer and polychelates were carried out in air. The catalytic activity of polychelates is discussed.

SYNTHESIS AND SPECTRAL STUDIES OF POLYAMIDE-PHOSPHATE ESTERS FROM PHOSPHINE-OXIDE-CONTAINING DIOLS WITH ARYL PHOSPHORODICHLORIDATES AND THEIR THERMAL AND FLAMMABILITY BEHAVIOUR

Polyamide-phosphate esters were synthesized by interfacial polycondensation of aryl phosphorodichloridates with the diols of phenoxaphosphine and phosphine oxide in the presence of a phase-transfer catalyst. The polymers were characterized by infra-red and 1H, 13C and 31P nuclear magnetic resonance (n.m.r.) spectroscopy. The molecular weights were determined by end-group analysis using 31P n.m.r. spectral data. The phenoxaphosphine-containing polymers showed superior thermostability and flame retardancy over the phosphine-oxide-containing polymers.

Dual switchable six-ring bent-core liquid crystals with azo linkages exhibiting B1 and B2 mesophases

A new series of asymmetric bent-core compounds were synthesised using azo linkages with equal as well as unequal terminal alkyl chains and their photo and electrical switching properties investigated. The mesomorphic properties were characterised using polarised optical microscopy, X-ray diffraction and differential scanning calorimetry. The lower homologues of the series of compounds show a B1 phase whereas higher homologues exhibit a B2 phase. The B2 phase shows an anticlinic-antiferroelectric switching behaviour during electro-optic measurements. The photo-switching properties of the azobenzene containing bent-core molecules were investigated using ultraviolet-visible spectroscopy. The trans to cis photo isomerisation was observed at 25 s whereas reverse processes took 14 h in chloroform.

Synthesis, single crystal growth, characterization and comparison of two new enone shifted chalcones and their NLO behaviour

Chalcone based materials are widely used in many industrial applications. The two new similar chalcone based single crystals, namely (E)-3-(4-(benzyloxy)phenyl)-1-(4-hydroxyphenyl)prop-2-en-1-one (Crystal A) and (E)-1-(4-(benzyloxy)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (Crystal B) were synthesized and grown as single crystals by slow evaporation solution growth technique in acetone. The structures of the grown crystals were solved and refined by single crystal XRD and this demonstrates that crystal A shows an orthorhombic system with a space group of Pca21 and crystal B crystallizes in a monoclinic system with a space group of C2/c. The morphology of the crystals A and B was predicted using WINXMORPH. The hyperpolarizability studies were carried out for the chalcone single crystals using density functional theory (DFT) - triply parameter hybrid model DFT/B3LYP using GAUSSIAN 03. The calculated first order hyperpolarizability was found as 0.1314 × 10−30 e.s.u. for crystal A and 0.188 × 10−30 e.s.u. for crystal B. The second harmonic generation was studied by Kurtz–Perry test. The comparison statement of the enone shifted material properties enumerates interesting results in all the studies.

Novel photo-crosslinkable flame retardant polyvanillylidene arylphosphate esters

A new class of photo-crosslinkable flame retardant arylphosphate ester polymers based on diarylidenecycloalkanone groups has been synthesized by polymerizing 2,5-divanillylidene cyclopentanone and 2,6-divanillylidenecyclohexanone with various arylphosphorodichloridates by interfacial polycondensation using a phase transfer catalyst. The resulting polymers were characterized by inherent viscosity, g.p.c., i.r., 1H, 13C, 31P n.m.r. spectroscopy. These polymers were studied for their photochemical and flame retardant properties. The divanillylidene cycloalkanone group in the chain function as photoactive centres while arylphosphate ester groups impart flame retardancy. The photo-crosslinking proceeds via 27π + 2π cycloaddition reaction of the divanillylidene cycloalkanone moieties. The crosslinking rate, thermal stability and flammability characteristics of the polymers increase with decrease in the size of the cycloalkanone ring.

Studies on thermotropic liquid crystalline polyphosphates containing photoreactive dual mesogens

A series of thermotropic liquid crystalline polyphosphates, containing photochromic molecules of stilbene in the backbone and substituted azobenzene in the side chain, were synthesized respectively. The inherent viscosity measurements were determined for all the polymers. The stability and char yield, Tg, Tm and Ti were investigated by thermal analysis. Polarizing optical microscopy of all the polymers exhibited birefringent melts with liquid crystalline behaviour. Variable temperature powder X‐ray diffraction techniques were performed for confirmation of textures. UV‐visible photolysis studies investigated the simultaneous behaviour of reactivity rates of crosslinking of stilbene units and isomerization, caused by azobenzene units in the main chain/side chain LCPs. Photoisomerization kinetics demonstrated the switching time rates for the trans‐cis conversion of the azobenzene unit. A model polymer was synthesized and compared for the effect of stilbene in the main chain. Dipole moment values were calculated for the simulated low molecular mass of the pendant substituents to predict the polarity using MOPAC 3D Pro.

Studies on photocrosslinkable‐cum‐flame retardant poly(benzylidene phosphoramide ester)s

Four series of photocrosslinkable-cum-flame retardant poly(benzylidene phosphoramide ester)s were synthesized from bis(4-hydroxy-3-methyoxybenzylidene) acetone, 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone, 2,6-bis(4-hydroxy-3- methoxybenzylidene)cyclohexanone and 2,7-bis(4-hydroxy-3-methoxybenzylidene) cycloheptanone with various arylphosphorodichloridates by interfacial polycondensation using a phase transfer catalyst. The resultant polymers were characterized by gpc, FTIR, 1H, 13C and 31P-NMR spectroscopy. Thermal behavior of the polymers was evaluated by differential scanning calorimetry and thermogravimetry. Flame retardant properties were ascertained by Limiting Oxygen Index. The photocrosslinking ability of the polymers was studied by ultraviolet spectroscopy. The crosslinking proceeds via 2π + 2π cycloaddition reaction of the benzylidene groups. The rate of crosslinking decreases with increase in the size of cycloalkanone ring, while the thermal stability increases with increase in the size of the alkanone ring.