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[en] Pyromellitic dianhydride (benzene-l,2,4,5-tetracarboxylic dianhydride) (1) was reacted with s-valine (2) in acetic acid and the resulting imide-acid [N,N'-(pyromellitoyl)- bis-s-valine] (4) was obtained in high yield. The compound (4) was converted to the N, N'-(pyromellitoyl)-bis-S-valine diacid chloride (5) by reaction with thionyl chloride. The polycondensation reaction of this diacid chloride with several aromatic diamines such as 1,4-phenylenediamine (6a), 4,4'-diaminodiphenyl methane (6b), 4,4'-diaminodiphenylsulfone (4,4'-sulfonyldianiline) (6c), 4,4'- diaminodiphenylether (6d), 2,4- diaminotoluene (6e), and 1,3-phenylenediamine (6f) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o cresol and trimethylsilyl chloride as an activating agent for diamines. The polymerization reactions were also performed with two other methods: low-temperature and high-temperature solution polycondensation in the presence of trimethylsilyl chloride. The polymerization reactions proceeded fast and produced a series of optically active poly(amide imide) s with good yield and moderate inherent viscosity of 0.25-0.43 dLg-1. One of the polymers (7b) showed high thermal resistance, the temperature of 5 % weight loss for (7b) was 490digC and the residual weight at 600digC was 76%. All of the above polymers were fully characterized by IR, elemental analysis and specific rotation. Some structural characterization and physical properties of these optically active poly(amide-imide)s are reported
[en] Inorganic polymeric materials comprise a very unique area science. These macromolecules which contain inorganic elements as part of their main chain structure or as pendent group, attract considerable attention as sceptically materials with unique properties and novel applications. Two main classes of these compounds: in organic and organometallic polymers, which represent a growing field of research, have found broad diverse applications. As, organic components with countless combinations are found in these classes of polymers they offer a wide range of interesting properties and applications. In this paper, the main properties of some more important classes of these compounds, including wholly inorganic-organic polymers, organometallic polymers and hybrid organic-inorganic networks are discussed on the basis of their structural features, and some examples of the novel applications of these materials are presented
[en] Polymers blends are a mixture of at least two plymers or more polymers with or without chemical bonding between them. This polymer blending is very practical to achieve commercially variable products through either unique properties or lower costing. When two or more polymers blend together the phase structure of the resulting material can be either miscible or immiscible.
[en] A combination of hydrophilic and hydrophobic characters in one macromolecule of a polymer provides amphiphilic behavior. Such unique properties, which have found significant interest, are exhibited by graft copolymers containing poly(ethylene oxide) (PEO) as side chains attached to the backbone (Scheme 1). They have greatly expanded a class of materials important for science and biomedicine. This review article describes the PEO graft copolymers prepared by a variety of synthetic procedures used for the atom transfer radical (co)polymerization (ATRP) (Scheme 2), i.e. directly by the grafting through, which is also named as the macromonomer method or by the grafting from technique, which requires the use of a multifunctional macroinitiator. Densely homografted copolymers also called molecular brushes were obtained by homopolymerization of PEO macromonomer (Scheme 3). The density of PEO grafts was decreased in the copolymerization of PEO macromonomer with a low molecular weight comonomer resulting in loosely grafted copolymers containing uniform PEO side chains (Scheme 4). Consequently, the copolymerization of two macromonomers yielded heterografted brushes (Scheme 5). In this case, the composition of copolymers was designed by the selection of proper comonomers with comparable (rM1 = rM2/rM1 ∼rM2) or different (rM1 > rM2, rM1 < rM2) reactivity ratios, which can form alternating/ random copolymers or spontaneous gradient of PEO chains along backbone, respectively. Using monofunctional macroinitiators with comb or linear composition for polymerization of PEO macromonomer resulted in comb-comb or semi-comb diblock copolymers. The reverse structures were also obtained, when the PEO graft copolymers were applied as the monofunctional macroinitiators. The use of polymeric multifunctional macroinitiators (graft or linear) in the polymerization of monomer or macromonomer led to the heterografted copolymers (Scheme 4) or more complexed double grafted copolymers (Scheme 3). The applications of the PEO graft copolymers in numerous fields are also presented to show their versatile potential. (author)
[en] The thesis dealt with the fine structural behaviour of twaron fibres, spun from the polymer poly (p-phenylene terephthalamide), due to physical treatments in the temperature range 75 to 984 kelvin (-198 to 675 degrees celsius). The treatments were annealing, cooling, cold ageing and vibratory milling. The structure was characterized by wide-angle x-ray diffraction (WAXS) and thermogravimetric analysis (TGA). The structural parameters included crystallinity, microparacrystal (mPc) sizes, net plane spacings, unit cell dimensions and mass stability. The TGA results indicated good mass stability up to 500 degrees celsius. The crystallinity and mPc sizes reached their maximum values after annealing the fibres at 425 degrees celsius (crystallinity increased by 5% and mPC sizes increased by approximately 40 to 50 %). After 500 degrees celsius, the crystallinity and mPC sizes dropped remarkably. Cooling the twaron fibres down to -198 degrees celsius did not affect the structure. Cold ageing of the fibres at -15 degrees celsius for periods up to 100 days, and cold ageing at -198 degrees celsius up to 48 hours did not affect the structure as well; however cold ageing at -198 degrees celsius for 120 hours caused a drop of 5% in the crystallinity and 10% in the mPc sizes. 35 refs., 28 figs., 9 tabs. (A.M.H.)
[en] This work assesses the overall reproducibility and accuracy of an x-ray computed tomography (CT) polymer gel dosimetry (PGD) system using a N-isopropyl-acrylamide (NIPAM) based polymer gel and investigated what effects the use of generic, inter-batch, and intra-batch gel calibration have on dosimetric and spatial accuracy. Overall excellent spatial and dosimetric accuracy was found with this system for generic, inter-batch calibration methods. (paper)
[en] Modification of the properties of polymers by ionising radiation has a great potential in the development of newer applications of these materials. The use of radiation polymerisation in rapid curing of coatings and printing inks, and in the manufacture of magnetic media has increased greatly over the last few years. Radiation grafting of biocompatible surfaces and functional groups onto substrates is also being used increasingly. A review of some of the recent radiation modifications in polymers has been presented in this paper. (author)
[en] A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as prevention of protein adsorption and anti-fouling activity. However, the characterization of polymer brush is still not straightforward since the brush layer is embedded between solid and water interface. One of limited number of analytical methods to reveal solid/water interface structures is neutron reflectivity (NR). We have been applying NR to reveal the problems related to polymer brush at solid/water interfaces and here present two subjects related to polymer brush. The first subject will be dynamic polymer brush which utilizes the surface segregation phenomena of copolymers with surface-active blocks for preparing polymer brush in spontaneous process. We have reported hydrophilic polymer brushes formed at the interface between water and hydrophobic elastomer by the segregation of amphiphilic diblock copolymers blended in the elastomer. In this system, while the hydrophilic block with high surface energy avoids air surface, upon contact with water the hydrophilic block segregates to cover the interface between hydrophobic elastomer and water. Surprisingly high density dynamic polymer brush at D_2O/polymer interfaces was observed by NR. The second subject will be evaluating inclusion kinetics of polyrotaxane formation using NR. A polyrotaxane is composed of a polymer chain and cyclic molecules such as polyethylene glycol (PEG) and cyclodextrin (CD). Inclusion complex formation of a polymer chain with cyclic molecules is an important step to synthesize polyrotaxanes. However, inclusion complex formation induces gelation or precipitation of the complex, and hence makes detailed observation of the reaction difficult. We fixed polymer chains on a substrate, which is polymer brush, and conducted in-situ time slice NR measurement. NR results showed that brush layer thickness gradually increases and reaches its plateau by inclusion complex formation, of which time scale depends on the concentration of cyclic molecules and other characteristics of the CDs.