The synthesis and characterization of the coating properties of liquid crystalline acrylic copolymers containing p -hydroxybenzoic acid as mesogenic group are described. The synthetic method involves the grafting of p-hydroxybenzoic acid onto acrylic copolymers, confirmed by characterization with IR and 1H NMR techniques. The presence of liquid crystal was assessed by observing optical textures under the polarizing microscope and by DSC and TGA. The coating properties such as flexibility, hardness, adhesion, drying time, viscosity, etc. of acrylic copolymers as well as of liquid crystalline acrylic copolymers were studied. The results showed that LC polymers have potential for coating applications. 相似文献
A liquid crystalline sequence-ordered polyester was prepared from isophthalic acid and 4-hydroxyphenyl 4-hydroxybenzoate in a 1:1 mole ratio. The local motions of this polymer were investigated by high-resolution solid-state 13C NMR and the results were compared to data obtained on liquid crystalline or semicrystalline random terpolyesters with very similar compositions. Whereas no motions of the hydroquinone rings could be detected below the glass-transition temperature of the semi-ordered polymer, the para-hydroxybenzoic acid units exhibit a certain degree of freedom in the temperature range between 450 K and 500 K. 相似文献
A series of new ionogenic liquid crystalline (LC) copolymers (A4CB-AA) was prepared by radical copolymerization of 4-(4-cyanobiphenyl-4′-yloxy)
butyl acrylate (A4CB) and acrylic acid (AA). The presence of the AA units do not prevent the development of the nematic phase,
which is typical of the initial cyanobiphenyl homopolymer. At a content of AA of 42–52 mol%, the copolymers produce the SAd type of mesophase, and this phenomenon is explained by an increased rigidity of the main chain due to the development of
intramolecular hydrogen bonds. By increasing the concentration of AA units higher than 55 mol%, the development of mesophase
is prevented, and the as-received copolymers are amorphous. A crucial role of intramolecular hydrogen bonds for the development
of the SA phase in the copolymers is proved by synthesizing and studying the copolymers, in which the same type of the mesogenic group
A4CB is preserved but the second component is provided by methyl ether of acrylic acid; such copolymers are able to produce
only a nematic phase. Studying orientation of LC A4CB-AA copolymers in the magnetic field by the method of wide-line 1H NMR spectroscopy allows one to calculate the temperature dependences of order parameter S and to advance a correct interpretation of experimental data.
Received: 8 January 1998 Accepted: 14 April 1998 相似文献
The formation of ordered structure in hydrogels derived from copolymers of hydrophilic and hydrophobic monomers with crystalline or liquid‐crystalline moieties is reviewed. The role of water in the formation of ordered structure and its influence on the thermal and mechanical properties of hydrogels are clarified. For example, by inducing a certain amount of water, an amorphous to crystalline transition occurs in gels of acrylic acid/alkyl acrylate copolymers. On the other hand, water induces a liquid‐crystalline (SmA) to liquid‐crystalline (SmI) transition in copolymers consisting of acrylic acid and 11‐(4′‐cyanobiphenyloxy)undecyl acrylate. These specific features regarding the formation of ordered structures in hydrogels might shed some light on the formation of ordered structure in biological tissues. 相似文献
The synthesis of a new liquid crystalline block copolymer consisting of a polystyrene block and a side-chain liquid crystalline siloxane block is reported. The synthetic approach described is based on the anionic polymerization of styrene and cyclic trimethyltrivinyltrisiloxane monomers, followed by functionalization of the siloxane block with side chain mesogens. The siloxane block has a Tg well below 25°C and is designed to exhibit a chiral smectic C* phase at room temperature. These block copolymers are the first side-chain liquid crystalline block copolymers which contain both a high Tg glassy block and a low Tg liquid crystalline block. 相似文献
A series of novel multi-arm star side-chain liquid crystalline (LC) copolymers with hyperbranched core moieties were synthesized by atom transfer radical polymerization (ATRP) using a multi-functional hyperbranched polyether as the initiator and chlorobenzene as the solvent. The multi-functional hyperbranched polyether initiator was prepared from poly(3-ethyl-3-(hydroxymethyl)oxetane) (PEHO) and 2-bromo-2-methylpropionyl bromide. The azobenzene side-chain liquid crystalline arms were designed to have an LC conformation of poly[6-(4-methoxy-4′-oxy-azobenzene)hexyl methacrylate] with different molecular weights. Their characterization was performed with 1H NMR, size exclusion chromatograph (SEC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The multi-arm star side-chain liquid crystalline copolymers exhibited a smectic and a nematic phase, and the phase transition temperatures from the smectic to the nematic phase and from the nematic to isotropic phase increased with increasing the molecular weight of the multi-arm star side-chain liquid crystalline copolymers from 1.78 × 104 to 9.07 × 104. 相似文献
In this study, a series of liquid crystalline diblock copolymers, composed of a soft poly(dimethylsiloxane) (PDMS) block with a de?ned length and a side-on liquid crystalline poly(3??-acryloyloxypropyl 2,5-di(4?-butyloxybenzoyloxy) benzoate) (P3ADBB) block with different lengths, are synthesised by the atom transfer radical polymerisation. The macromolecular structures, liquid crystalline properties and the microphase-separated morphologies of the diblock copolymer are investigated by 1H NMR, FT-IR, GPC, POM, DSC and TEM. The results show that the well-de?ned diblock copolymers (PDMSn-b-P3ADBBm) possess four different soft/rigid ratios (n = 58, m = 10, 25, 42, 66) and relatively narrow molecular distributions (PDI ≤ 1.30). P3ADBB blocks of the copolymers show nematic sub-phases, which are identical to the mesomorphic behaviour of the homopolymer P3ADBB. After being annealed at 90°C in a vacuum oven for 48 h, the copolymers form a lamellar morphology when m = 10 and morphologies of PDMS spheres embedded in P3ADBB matrix when m = 25, 42 and 66. 相似文献
A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. ~1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent (for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges. Theintroduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinityof the polymers but retain the liquid crystalline characteristics. 相似文献
Summary: The one step synthesis of a series of branched azobenzene side‐chain liquid‐crystalline copolymers by the self‐condensing vinyl copolymerization (SCVCP) of a methyl acrylic AB* inimer, 2‐(2‐bromoisobutyryloxy)ethyl methacrylate (BIEM), with the monomer 6‐(4‐methoxy‐azobenzene‐4′‐oxy)hexyl methacrylate (M), by atom transfer radical polymerization (ATRP) in the presence of CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as a catalyst system, and in chlorobenzene solvent, is reported. The degree of branching (DB), and the molecular weights and polydispersities of the resultant polymers were determined by NMR spectroscopy and size exclusion chromatography, respectively. The phase behaviors of the branched copolymers were characterized by differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The degree of branching of the branched copolymers could be controlled by the comonomer ratio in the feed and influenced their liquid‐crystal properties. Liquid‐crystal properties were not exhibited when the comonomer ratio was low. Comonomer ratios greater than 8 gave polymers with a lower number of branches, which exhibited both a smectic and a nematic phase.
A polarized optical micrograph of the smectic phase texture of a polymer synthesized here with a higher comonomer feed ratio (magnification × 400). 相似文献
Methods of molecular hydrodynamics and optics were used to study properties of aqueous solutions of acrylamide copolymers
with acrylic acid. Dependences of the molecular characteristics of the copolymers on their synthesis conditions were determined
and conditions were found in which the process of radical copolymerization of acrylamide with acrylic acid yields water-soluble
carboxyl-containing acrylamide copolymers with molecular masses not exceeding 4×104 Da. 相似文献
Polyaryl esters of moderate molecular weights were prepared by the direct polycondensation reaction of hydroxybenzoic acids and its derivatives with hexachlorocyclotriphosphatriazene (also known as phosphonitrilic chloride trimer, PNC) as a condensing agent in pyridine. Copolymerization of p-hydroxybenzoic acid with several hydroxybenzic acid derivatives was carried out to improve the processability of the polymer of p-hydroxybenzoic acid, which yields fusible and soluble copolymers of high inherent viscosities. Polymer solubility and thermal behavior were examined. 相似文献
The structure and thermodynamic properties of atactic and isotactic acrylic and methacrylic polymers containing 16–18 carbon atoms in the n-aliphatic side chains, and of copolymers of hexadecyl acrylate with isopropyl acrylate were studied by means of x-ray and differential thermal analysis. The crystallization of branched acrylic and methacrylic polymers and of acrylic copolymers proceeds in the form of a hexagonal crystal, regardless of the configuration of the backbone chain. Methods of ordering branched macromolecules are proposed, and the melting points, heats and entropies of fusion determined. The role of flexibility of the backbone chains in ordering and the crystallization processes was determined. In the case of poly(n-alkyl acrylates) the backbone chain is involved in the crystalline lattice; this is not the case in methacrylates and copolymers of hexadecyl acrylate with isopropyl acrylate. Some similarity was assumed between the structure of biopolymers and synthetic branched polymers. 相似文献
Three generations of dendritic polyester macromolecules based on 5-hydroxyisophthalic acid were synthesized by the divergent growth approach. The characterization of dendritic fragments was performed using a combination of 1H NMR, 13C NMR spectroscopy and elemental analysis. The dendritic hydrogen-bonded supramolecular liquid crystalline complexes were prepared from different generation of dendritic acids and stilbazole derivative containing pyridyl units. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) were used for investigation of the liquid crystalline properties of the hydrogen-bonded dendritic supramolecular complexes. 相似文献