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1.
Malcolm B. Polk Mahendra Nandu Metha Phingbodhipakkiya 《Journal of polymer science. Part A, Polymer chemistry》1986,24(8):1923-1931
The syntheses and characterizations of poly(oxy-trans-1,4-cyclohexyleneoxycarbonyl-1,4-bicyclo[2.2.2]octylenecarbonyl) (I) and poly(oxy-trans-1,4-cyclohexyleneoxycarbonyl-1,4-bicyclo[2.2.2]octylenecarbonyl-co-oxy-trans-1,4-cyclohexyleneoxysebacoyl) (II) are described. The polymer systems were characterized by infrared spectroscopy, proton magnetic resonance spectroscopy, solution viscosity, and differential scanning calorimetry. The random copolyester prepared from 1:0.65:0.35 mol of trans-1,4-cyclohexanediol, bicyclo[2.2.2]octane-1,4-dicarbonyl chloride, and sebacoyl chloride, respectively, formed a birefringent fluid state in the melt. 相似文献
2.
Malcolm B. Polk Venu Kannappan Issifu Harruna Metha Phingbodhipakkiya 《Journal of polymer science. Part A, Polymer chemistry》1986,24(5):931-946
Poly[oxy-2,2′-diphenyleneoxyisophthaloyl-b-oxy(2-methyl-1,3-phenylene)oxyterephthaloyl] I, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-methyl-1,3-phenylene)oxyterephthaloyl] II, poly(oxy-2,2′-diphenyleneoxyisophthaloyl-b-oxy-2,2′-diphenyleneoxyterephthaloyl) III, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-methyl-1,4-phenylene)oxyterephthaloyl] IV, poly[oxy2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-chloro-1,4-phenylene)oxyterephthaloyl] V, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-co-oxy(2-chloro-1,4-phenylene)oxyterephthaloyl] VI, and poly[oxy-2,2′-diphenyleneoxyterephthaloyl-co-oxy(2-methyl-1,4-phenylene)oxyterephthaloyl] VII have been synthesized and characterized. Random copolyester VI appears to form a birefringent fluid phase above the melting temperature. 相似文献
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4.
Malcolm B. Polk Harold D. Banks Fidelis Onwumere N. Venkatasubramanian Mahendra Nandu Metha Phingbodhipakkiya Edward T. Samulski 《Journal of polymer science. Part A, Polymer chemistry》1988,26(9):2405-2422
A number of thermotropic copolyesters which contain the bicylo[2.2.2]octane ring system have been synthesized. Because of the stiffening effect of the bicyclo[2.2.2]octane group on the chain, the sebacoyl spacer was used to obtain meltable compositions. 相似文献
5.
This work presents the synthesis of magnetite nanoparticle (MNP) coated with poly(N,N-diethylaminoethyl methacrylate)-b-poly(N-isopropyl acrylamide-st-thiolactone acrylamide) (PDEAEMA-b-P(NIPAAm-st-TlaAm) copolymer and its use in controlled drug release and bio-conjugation. TlaAm units in the copolymer were ring-opened with various alkyl amines to form thiol groups (-SH), followed by thiol-ene coupling reactions with acrylamide-coated MNP and then quaternized to obtain cationic copolymer-MNP assemblies (the size <?200 nm/cluster). The use of alkyl amines having various chain lengths (e.g., 1-propylamine, 1-octylamine, or 1-dodecylamine) in the nucleophilic ring-opening reactions of the thiolactone rings affected their magnetic separation ability, water dispersibility, and release rate of doxorubicin model drug. In all cases, when increasing the temperature, they showed a thermo-responsive behavior as indicated by the decrease in hydrodynamic size and the accelerated drug release rate. These copolymer-MNP assemblies could be used as a novel platform with thermal-triggering controlled drug release and capability for adsorption with any negatively charged biomolecules. 相似文献
6.
Calculated energy profiles for the reactions of neutral Nb(2) and Nb(3) metal clusters with CO, D(2), N(2), and O(2) are presented. In each reaction path, both a physisorption energy minimum, where the reactant remains intact, and a chemisorption energy minimum, where the reactant has dissociated, are calculated and linked by saddle points. We calculate branching ratios for the forward (dissociative) and reverse reactions which we compare with the experimental kinetic data. It is found that a combination of average thermal energies and barrier heights leads to wide variation in branching ratios which compares favourably to previously determined experimental reaction rates. 相似文献
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Boonjira Rutnakornpituk Uthai Wichai Tirayut Vilaivan Metha Rutnakornpituk 《Journal of nanoparticle research》2011,13(12):6847-6857
Surface modification of magnetite nanoparticles (MNP) with a covalently bonded poly(4-vinylpyridine) (P4VP) by surface-initiated
atom transfer radical polymerization (ATRP) is reported in this article. MNP was first prepared via thermal decomposition
of Fe(acac)3 and grafted with an ATRP initiator on its surface. ATRP of 4-vinylpyridine was then initiated from the MNP surface in the
presence of CuBr/PMDETA (1,1,4,7,7-pentamethyldiethylenetriamine) catalytic complex in dioxane. FTIR in combination with photocorrelation
spectroscopy (PCS), thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM) techniques indicated the growth
of P4VP on the particle surface with increasing ATRP reaction time. Transmission electron microscopy (TEM) disclosed that
the average particle size was 8 nm in diameter with some nanoaggregation observed. The PCS results revealed that decreasing
the solution pH enhanced the particle dispersibility because of the positive charge repulsion of the protonated P4VP on the
particle surface. TGA was also performed to elucidate the composition of P4VP shell and magnetite core in the hybrid material. 相似文献
9.
Pawinee Theamdee Rakchart Traiphol Boonjira Rutnakornpituk Uthai Wichai Metha Rutnakornpituk 《Journal of nanoparticle research》2011,13(10):4463-4477
We here report the synthesis of magnetite nanoparticle (MNP) grafted with poly (ethylene glycol) methyl ether methacrylate
(PEGMA)-azobenzene acrylate (ABA) statistical copolymer via atom transfer radical polymerization (ATRP) for drug entrapment
and photocontrolled release. MNP was synthesized via thermal decomposition of iron (III) acetylacetonate in benzyl alcohol
and surface functionalized to obtain ATRP initiating sites. Molar compositions of the copolymer on MNP surface were systematically
varied (100:0, 90:10, 70:30, and 50:50 of PEGMA:ABA, respectively) to obtain water dispersible particles with various amounts
of azobenzene. The presence of polymeric shell on MNP core was evidenced by transmission electron microscopy (TEM). Drug loading
and entrapment efficiencies as well as drug release behavior of the copolymer–MNP complexes were investigated. It was found
that when percent of ABA in the copolymers was increased, entrapment and loading efficiencies of prednisolone model drug were
enhanced. Releasing rate and percent of the released prednisolone of the complex exposed in UV light were slightly enhanced
as compared to the system without UV irradiation. This copolymer–MNP complex with photocontrollable drug release and magnetic
field-directed properties is warranted for further studies for potential uses as a novel drug delivery vehicle. 相似文献
10.
Dryza V Addicoat MA Gascooke JR Buntine MA Metha GF 《The journal of physical chemistry. A》2005,109(49):11180-11190
We have used photoionization efficiency spectroscopy to determine the ionization potentials (IP) of the tantalum-carbide clusters, Ta3Cn (n = 1-3) and Ta4Cn (n = 1-4). The ionization potentials follow an overall reduction as the number of carbon atoms increases; however, the trend is not steady as expected from a simple electrostatic argument. Instead, an oscillatory behavior is observed such that clusters with an odd number of carbon atoms have higher IPs and clusters with an even number of carbon atoms have lower IPs, with the Ta4C4 cluster exhibiting the lowest IP. Excellent agreement is found with relative IPs calculated using density functional theory for the lowest energy structures, which are consistent with the development of a 2 x 2 x 2 face-centered nanocrystal. This work shows that IPs may be used as a reliable validation for the geometries of metal-carbide clusters calculated by theory. The variation in IP can also be interpreted qualitatively with application of a simple model based upon isolobal frontier orbitals. 相似文献