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101.
Patrícia P. C. Sartoratto I. Valria P. Yoshida 《Journal of polymer science. Part A, Polymer chemistry》1992,30(11):2333-2340
In this work several polyorganosilylenes were synthesized including homo-and copolymers containing SiMe2 and SiPh2 units. A Wurtz-type coupling reaction of the respective dichlorodiorganosilanes with sodium metal, varying the Ph2SiCl2/Me2SiCl2 ratio was the chosen synthesis method. Products with different characteristics for solubility, structure (cyclic or linear), composition, and molecular weight distribution could be obtained depending on the comonomer ratios employed. The polysilane derivatives were characterized by infrared spectroscopy (IR), proton nuclear magnetic resonance (1H-NMR), and gel permeation chromatography (GPC). Valuable information related to the comonomers' reactivities was obtained, such as molecular weight distribution, composition, and relationships between yields of soluble, insoluble, and cyclic materials of each polycondensation reaction. © 1992 John Wiley & Sons, Inc. 相似文献
102.
Highly hydrophobically modified (with n-dodecylamide chain) linear poly(acrylic acid)s (HHMPAAH) and poly(sodium acrylate)s (HHMPAANa) with various degrees of grafting
(τ) were synthesized and used as emulsifiers of the n-dodecane/water system. The type of emulsion, oil in water (O/W) or water in oil (W/O), was investigated as a function of
the polymer chemical structure (τ, salt or acid form of the copolymer) and aqueous phase electrolyte concentration (NaNO3). Increasing τ and/or salt concentration was found to favor the formation of inverse emulsions. Direct liquid–liquid dispersions
are more likely to form with poly(sodium acrylate)s than with poly(acrylic acid)s. Hence, field variables such as τ, pH and
ionic strength are relevant parameters to control emulsion type. Moreover, a balanced polyelectrolyte neither soluble in oil
nor in water was synthesized for the first time. With this original emulsifier, the dispersion type was found to change from
O/W to W/O with polymer salting out. The work provides convenient model system for fundamental studies of polymer conformation
at liquid–liquid interfaces.
Received: 31 March 1998 Accepted: 30 April 1998 相似文献
103.
G. Glöckner 《Chromatographia》1987,23(7):517-524
Summary Prerequisite of quantitative evaluation in chromatography is equivalence of sample composition and detector signal. This includes
complete retention and proper elution of all sample constituents. In polymer HPLC, complete retention requires a poor starting
eluent, a sufficiently active column, and a low ratio of injection volume to column volume. On small pore columns, insufficient
retention caused the polymer to elute either in the interstitial volume (sample exclusion), together with the sample solvent,
or immediately after the solvent plug.Stat-copoly(styrene/ethyl methacrylate) samples are more difficultly retained thanstat-copoly(styrene/acrylonitrile) specimes. With the former copolymer it could be shown that incomplete retention did not cause
sample demixing. In order to gain complete retention, non-exclusion HPLC of polymers should be performed with columns whose
solvent volume is at least 50 times as large as the injection volume. This consequence is of practical importance in chromatographic
cross-fractionation where rather large volumes of SEC eluate are injected into the apparatus for gradient HPLC. 相似文献
104.
Amphiphilic diblock copolymers consisting of a hydrophobic polystyrene block (PS) and a hydrophilic poly(ethylene oxide)
block (PEO) with block sizes of 1000 or 3000 g/mol for both blocks were studied at the air/water and toluene/water interface.
Measurements of the film pressure π of spread monolayers at the water surface reveal two limiting regimes of the π−a
m isotherms, in which the mean molecular area a
m is determined either by the size of the hydrophilic or the hydrophobic blocks of the PS-PEO molecules. The interfacial activity
of the block copolymers at the toluene/water interface was studied by measuring the interfacial tension σ over a wide range
of concentrations. Pronounced differences in the temperature dependence of the interfacial tension were observed, depending
mostly on the block length of the hydrophilic PEO block. From the temperature dependence of σ it is inferred that for the
block copolymers with the PEO block size of 3000 g/mol the phase inversion temperature (PIT) is well above 60 °C while for
those with a PEO block size of 1000 g/mol the PIT is below or near 25 °C in the toluene/water system.
Received: 5 February 1998 Accepted: 16 February 1998 相似文献
105.
Lys(z)-NCA was synthesized in the presence of triphosgene, amphiphilic triblock copolymers poly(N^c-CBZ-Lysine)-PEG-poly(N^c-CBZ-Lysine) were synthesized in DMF using amino-end ended PEG as initiator with the mechanism of anion ring opening polymerization. The structures of block copolymers were characterized by IR, ^1H-NMR,GPC and DSC. The results showed triblock copolymers with expected structure and low polydispersity in molecular weight could be synthesized by this method. At the same time, the self-assembling behaviors of block copolymer were investigated by TEM. A novel helical aggregates were found to be formed in DMF. Because of biocompatibility of two components of block copolymers, these block copolymers have potential applications in the field of biomaterials. 相似文献
106.
Marek Daszkiewicz Zbigniew Staszak Adam Pietraszko Wiesława Bronowska Maria Cieślak-Golonka 《Structural chemistry》2006,17(6):599-608
Two polymeric complexes: catena(μ-CrO4-O,O′)[Co(HIm)3H2O] (1) and catena(μ-CrO4-O,O′)[Co0.43Ni0.57(HIm)3H2O] (2) (where HIm=imidazole) with a cis-bridging coordination mode of the CrO4
2− anion have been synthesized and characterized by X-ray and spectroscopic methods. These crystals were isolated from nine
systems of varying reagent molar ratios and three excluding anions: Cl−, NO3
− and SO4
2− exclusively as mer [M(HIm)3O3]-type isomers. The unit cell of these isostructural complexes (monoclinic crystal system P21
/n) contains two independent helixes, left- and right handed, stabilized by intrahelical and interhelical hydrogen bonding and
π–π interaction between pairs of the imidazole rings from neighbouring helixes. The Raman spectra at 77 K of 1 and 2 deconvoluted into lorentzian components revealed the block-type polymeric structure of the complexes. Moreover, the solution
studies at millimolar concentrations of 1 and 2 indicated their complete decomposition in water. Four K electronic spectral analysis of the crystals (band deconvolution
into gaussian components) enhanced with the data obtained in the polarized light allowed for assignment of the bands to the
respective d–d transition (D4h symmetry). It was found that the metallic centres are independently absorbing species, which supports the suggestion of a
block-type structure of the polymers. The respective crystal field parameters for Co and Ni were calculated. 相似文献
107.
Shaheen Motala-Timol 《European Polymer Journal》2007,43(7):3042-3049
The synthesis of ABA triblock copolymers of the type PDMAEMA-PCL-PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br-PCL-Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks. 相似文献
108.
为了探索生物基乙二醇中的1,2-丁二醇(1,2-BDO)作为共聚单体对生物基聚对苯二甲酸乙二醇酯(PET)的结晶行为和力学性能的影响。 本文合成了生物基PET均聚物和不同1,2-BDO共聚单元摩尔分数的系列生物基PET共聚物(共聚单体摩尔分数分别为2.0%、2.7%和5.6%),并采用傅里叶变换红外光谱仪(FTIR)、差示扫描量热仪(DSC)和力学测试等技术手段研究了其结晶行为和力学性能。 结果表明,随着1,2-BDO共聚单元摩尔分数的增加,PET共聚物的熔融温度、结晶速率及结晶度均明显降低,表明1,2-BDO共聚单体的引入破坏了PET分子链的规整性,阻碍了PET链段的结晶。 PET材料的拉伸强度随着1,2-BDO共聚单元摩尔分数的增加而降低,而弯曲强度和弯曲模量略有升高。 相似文献
109.
Mingzhu Liu Rongshi Cheng Jingjia Wu Cheng Ma 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3181-3186
A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO3) (1.08, 5.0 × 10?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: Rp = Kkd [STOH] [Ce4+] + Kkpkd/kt[STOH][M], where K, kd, kp, and kt are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc. 相似文献
110.
Qin Ren Hong Jin Zhang Xiao Kang Zhang Bao Tong Huang 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):847-851
To get hydrogenated polybutadiene-polymethyl methacrylate (HPB-b-PMMA) block copolymer to be used as a compatibilizer for blends of polyolefin/polar polymer, PB-b-PMMA was synthesized by anionic-free radical mechanism transformation polymerization. Selective extraction, gradient elution thin layer chromatography, and oil-oil emulsion separation techniques were tried to attempt to separate the copolymerization products. Hydrogenation of the PB sequence in PB-b-PMMA yielded HPB-b-PMMA. The compatibilizing function of PB-b-PMMA was shown in blending experiments. © 1993 John Wiley & Sons, Inc. 相似文献