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1.
We report matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and off-line coupling of size-exclusion chromatography with MALDI-TOFMS analysis (SEC/MALDI-TOFMS) methods for the detailed characterization of poly[(R,S)-3-hydroxybutyrate-co-L-lactic acid], P[(R,S)-3HB-co-LA], and poly[(R,S)-3-hydroxybutyrate-co-epsilon-caprolactone], P[(R,S)-3HB-co-CL], copolymer samples which are expected to be used in special medical application as scaffolds for cartilage and soft tissue engineering. The novel copolyesters contained randomly distributed (R,S)-3-hydroxybutyrate structural units, were synthesized by transesterification of the corresponding homopolymers, i.e. atactic poly[(R,S)-3-hydroxybutyrate], a-PHB, and poly(L-Lactide) (PLLA) or poly(epsilon-caprolactone) (PCL), respectively. The MS methods used for the characterization of the resulting polydisperse copolyester samples were supported by classical methods (NMR, SEC). The structures of individual copolyester macromolecules, including end-group chemical structures, were established using initially MALDI-TOFMS and then SEC/MALDI-TOFMS. The compositions of the copolyesters were determined by two methods, namely based on 1H NMR and MALDI-TOF spectra. The two sets of values showed good agreement. The sequence distribution was determined using the signal intensities of individual copolyester macromolecules, which appeared in MALDI-TOF mass spectra. Furthermore, sequence analysis gave information about the degree of transesterification. The copolyesters synthesized, with only one exception, were demonstrated to be almost random, which implies that the ester-ester exchange was close to completion.  相似文献   

2.
Racemic and optically active 3-pyrrolidinecarboxylic acids (β-proline) were synthesized, and their polymers, poly[(RS)-β-proline] and poly[(R)-β-proline], were prepared by the polycondensation reaction of the p-nitrophenyl esters. Model compounds, N-cyclopentylcarboxylic acid pyrrolidide and N-cyclopentylcarbonyl-(R)-3-pyrrolidinecarboxylic acid pyrrolidide, were synthesized to elucidate the conformation of the polymer. The solution properties of poly[(R)-β-proline] and the model compounds were investigated by means of circular dichroism (CD) and NMR spectroscopy. The spectral patterns of the polymer and model compounds were similar in various solvents. Poly[(R)-β-proline] and poly[(RS)-β-proline] showed identical NMR spectra. These results suggest that poly[(R)-β-proline] may exist in a random conformation consisting of mixtures of cis and trans amide bonds. The conformational study of cyclopentanecarboxylic acid pyrrolidide by NMR spectroscopy with a shift reagent, Eu(fod)3, in CDCl3 implied that the plane containing the amide group bisects the cyclopentane ring. This suggests that each amide plane in the polymer in chloroform may also bisect the pyrrolidine ring.  相似文献   

3.
The preparation, fractionation and characterisation of synthetic cyclic polysiloxanes (R(CH3)SiO)x are reviewed. Particular emphasis is given to the cyclic poly(dimethylsiloxanes) (PDMS) (R is CH3) cyclic poly(phenylmethylsiloxanes)(PPMS) (R is C6H5) and cyclic poly(vinylmethylsiloxanes) (PVMS) (R is CH2=CH). The application of high performance liquid chromatography (HPLC) and analytical and preparative gel permeation chromatography (GPC) to the preparation and characterisation of cyclic polysiloxanes is discussed. The methods include preparation of sharp fractions of relatively high molar mass cyclic polymers (with heterogeneity indices typically ca. 1.05) and comparison of the GPC and retention volumes of cyclics with the corresponding linear polymers. Investigations of the cyclic polymers prepared have been made using a number of experimental methods and techniques. These include dilute solution viscometry and low angle neutron scattering. Comparisons are drawn between cyclic PDMS and other cyclic polysiloxanes and also between cyclic polysiloxanes and the corresponding commercially-important linear polymers.  相似文献   

4.
Soap-free emulsion polymerization was extended to preparation of monodisperse poly(methyl methacrylate) (PMMA) particles incorporating rhodamine 6G (R6G) fluorescent molecules. The polymerization was conducted in the presence of an anionic monomer, p-styrenesulfonate (NaSS), which improved dispersion stability of the polymer particles. NaSS concentrations was ranged up to 2 mol/m3 H2O in the polymerization at 0.5 kmol/m3 H2O methyl methacrylate (MMA) monomer and 5 mol/m3 H2O potassium persulfate (KPS) initiator for R6G concentrations from 0.1 to 10 mol/m3-polymer. At R6G concentrations lower than 1.0 mol/m3-polymer, PMMA particles were highly monodisperse and incorporated most R6G molecules. The average sizes of PMMA particles were in a rage of 160-300 nm, and decreased with the concentration of NaSS. The high monodispersity of the particles enabled the fabrication of colloidal crystals of the particles with a vertical deposition method.  相似文献   

5.
The repeating guest units of poly‐(R)‐ 2 were selectively encapsulated by the self‐assembled capsule poly‐ 1 possessing eight polymer side chains to form the supramolecular graft polymer (poly‐ 1 )n?poly‐(R)‐ 2 . The encapsulation of the guest units was confirmed by 1H NMR spectroscopy and the DOSY technique. The hydrodynamic radius of the graft polymer structure was greatly increased upon the complexation of poly‐ 1 . The supramolecular graft polymer (poly‐ 1 )n?poly‐(R)‐ 2 was stably formed in the 1:1 host–guest ratio, which increased the glass transition temperature by more than 10 °C compared to that of poly‐ 1 . AFM visualized that (poly‐ 1 )n?poly‐(R)‐ 2 formed the networked structure on mica. The (poly‐ 1 )n?poly‐(R)‐ 2 gelled in 1,1,2,2‐tetrachloroethane, which led to fabrication of distinct viscoelastic materials that demonstrated self‐healing behavior in a tensile test.  相似文献   

6.
The preparation, (1)H, (13)C, and (19)F NMR structural characterization as well as with DFT-based theoretical calculations of stable dialkyl ether/poly(hydrogen fluoride) complexes are reported. Dimethyl ether/poly(hydrogen fluoride) (DMEPHF), are stable complexes of particular interest and use. The DFT calculations, that are in agreement with NMR data, suggest a cyclic poly(hydrogen fluoride) bridged structure for DMEPHF. The complex, DME-5 HF was found to be a convenient and effective new fluorinating agent with the ease of workup and applied to several fluorination reactions, such as the hydrofluorination and bromofluorination of alkenes, and fluorination of alcohols giving good to excellent yield with high selectivity. Homologous dialkyl ether/poly(hydrogen fluoride) (R(2)O/[HF](n,), R = Et, nPr) systems are also stable and suitable for fluorination reactions.  相似文献   

7.
通过添加对映体拆分剂,合成了4种含膦手性的丙炔胺磷酸酯单体[HC帒CC H2NH(PO)R1R2].单体1,R1=OPh,R2=NC4H7COOCH3;单体2,R1=OPh,R2=NC4H7COOCH2CH3;单体3,R1=OPh,R2=NC4H7-COOC(CH3)3;单体4,R1=Ph,R2=NC4H7COOC(CH3)3].1H-NMR和31P-NMR表征可知对映体(单体1)不能被拆分剂拆分,而单体2、单体3、单体4通过拆分剂可以制得单一手性的磷化合物.以(nbd)Rh+[η6-C6H5B--(C6H5)3]为催化剂,以三氯甲烷为溶剂成功得到聚合物分子量范围在0.4×10-4~0.7×10-4,分子量分布在1.26~1.98范围的3种含手性膦侧基的丙炔胺类聚合物.比旋光度([α]D)、圆二色谱(CD)对聚合物的不同侧基及温度对光学活性的影响表明,聚合物具有良好的光学活性且能够形成单一方向的螺旋构象,说明膦手性在构建螺旋聚合物具有重要作用.  相似文献   

8.
End‐functionalized poly(phenylacetylene)s were synthesized by the polymerization of phenylacetylene (PA) using the well‐defined palladium catalysts represented as [(dppf)PdBr(R)] {dppf = 1,1′‐bis(diphenylphosphino)ferrocene}. The Pd catalysts having a series of R groups such as o‐tolyl, mesityl, C(Ph)?CPh2, C6H4o‐CH2OH, C6H4p‐CN, and C6H4p‐NO2 in conjunction with silver triflate polymerized PA to give end‐functionalized poly(PA)s bearing the corresponding R groups in high yields. The results of IR and NMR spectroscopies and MALDI‐TOF mass analyses proved the introduction of these R groups at one end of each polymer chain. The poly(PA) bearing a hydroxy end group was applied as a macroinitiator to the synthesis of a block copolymer composed of poly(PA) and poly(β‐propiolactone) moieties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010  相似文献   

9.
Linear gradient elution experiments were carried out on monolithic anion-exchange chromatography (AEC) with oligo-DNAs of various sizes (4-50mer, molecular weight M(W)=1200-15,000) and compositions in order to investigate the retention mechanism. The binding site (B) values as well as the peak salt elution concentration I(R) values were determined. The B values determined for the monolithic AEC were similar to the values for non-porous AEC and porous AEC. The B value increased linearly with the number of charges (bases) of single-strand DNA when M(W) is less than ca. 3600 (12mer). When M(W) is greater than 6000, the slope of B versus M(W) decreased, and became very small at M(W)>30,000. The I(R) value also increased linearly with M(W) for M(W)<6000, and slightly with M(W) for M(W)>10,000. It was shown that a very difficult separation of a single-strand 50mer poly(T) and a double-strand 50mer poly(A) and poly(T) was accomplished within 10 min by using a very shallow gradient at a high initial salt concentration (0.5M) and a high flow-velocity (2.7 cm/min).  相似文献   

10.
Biodegradable P[(R,S)-3HB-co-LA] and P[(R,S)-3HB-co-CL] copolyesters for special medical application, i.e. as scaffolds for cartilage and soft tissue engineering, were synthesized by transesterification of the corresponding homopolymers, i.e. a-PHB and poly(L-lactide) or a-PHB and poly(e-caprolactone), respectively. The carried out biological studies emphasized the biocompatibility of the copolymer PHBV/a-PHB, in for its using in the manufacturing of the haemostatical dressings.  相似文献   

11.
A series of telechelic oligo[(R,S)‐3‐hydroxybutyrate]‐diols (PHB‐diols) was synthesized from ethyl (R,S)‐3‐hydroxybutyrate (ethyl (HB)) and four different aliphatic diols, namely, 1,4‐butanediol, 1,6‐hexanediol, 1,8‐octanediol and 1,10‐decanediol by transesterification and condensation in bulk. The structures of the synthesized oligomers were confirmed by 1H NMR spectroscopy and MALDI‐TOF mass spectroscopy. The use of 1,4‐butanediol results in an oligoester with hydroxyl functionality of approximately 2. In the case of the higher aliphatic diols, the number average functionalities were found to be lower than 2. These differences were ascribed to side reactions which occur during polymerization, yielding unreactive end groups. Other novel families of biodegradable poly(ester‐urethane)s were synthesized either from PHB‐diol alone, or PHB‐diol mixed with poly(ε‐caprolactone)‐diol (PCL‐diol), poly(butylene adipate)‐diol (PBA‐diol) or poly(diethylene glycol adipate)‐diol (PDEGA‐diol). In each case, 1,6‐hexamethylene diisocyanate was used as a nontoxic connecting agent. The homopolymers prepared from PCL‐diol, PBA‐diol and PDEGA‐diol were also synthesized for the sake of comparison. All the prepared copolymers possess high molecular weight with glass transition temperature (Tg) values varying from –54 to –23°C. Some of the prepared copoly(ester‐urethane)s are partially crystalline with melting temperatures (Tm's) varying from 37 to 56°C.  相似文献   

12.
Novel conjugated ionic polymer was prepared by the polymerization of 2-ethynylpyridine with propargyl tosylate in refluxing methyl alcohol. The polymerization proceeded well in homogeneous manner to give a relatively high yield of polymer. The resulting poly(2-ethynylpyridinium tosylate) having propargyl side chain [poly(EPT-P)] were hygroscopic and soluble in water, methyl alcohol, DMF, and DMSO. The inherent viscosities of the polymers were in the range of 0.08-0.29dL/g. Instrumental analyses using NMR, IR, and UV-visible spectroscopies and elemental analyses indicated that the resulting poly(EPT-P) have a conjugated ionic polymer backbone carrying N-propargyl-2-pyridinium tosylate. Thermal and electro-optical properties of the polymers were also studied.  相似文献   

13.
锗桥连茚及取代茚配体相继与丁基锂及ZrCl4作用,生成锗桥连茚基及取代茚基锆化合物Me2Ge(2-R1-4-R2-Ind)2ZrCl2[R1=R2=H(1);R1=Me,R2=H(2);R1=Me,R2=Ph(3)].化合物1-3均为内消旋和外消旋异构体的混合物,通过多次重结晶得到化合物1和2的纯外消旋异构体及化合物3的内消旋异构体.由元素分析和1H NMR谱表征了化合物的分子结构.研究了在甲基铝氧烷(MAO)的助催化下,化合物1-3对乙烯和丙烯聚合的催化性能.由锗桥连茚基化合物1-3得到的聚乙烯的分子量分布比一般茂金属催化剂略宽.内消旋和外消旋异构体的混合物(3)由于两个催化活性中心不等同而使得到的聚乙烯的分子量分布相当宽.外消旋异构体1和2催化丙烯聚合得到高等规聚丙烯.  相似文献   

14.
Optically pure methyl, ethyl, isopropyl, and benzyl (R)-malolactonate were prepared from (S)-(-)-malic acid and were polymerized in the bulk with tetraethylammonium benzoate as the initiator to yield high-molecular-weight, crystalline polymers. The optical purity of methyl and benzyl malolactonate was determined by 1H NMR spectroscopy of the β-lactone complexed with a chiral europium shift reagent. Enantiomeric excesses of 100% were found (the experimental error was 3%). Optically active poly(β-malic acid) was obtained from optically active poly[benzyl (S)-malate] by catalytic hydrogenolysis of the pendent benzyl esters. Ethyl and benzyl (R)-malolactonate were also copolymerized, and the benzyl esters of the resulting copolymer were converted into carboxylic acid units by hydrogenolysis.  相似文献   

15.
The synthesis and “living” cationic polymerization of 3-fluoro-4′-(11-vinyloxyundecany-loxy)-4-biphenylyl (2R,3S)-2-fluoro-3-methylpentanoate ( 12-11 ) and 3-fluoro-4′-(8-vi-nyloxyoctyloxy)-4-biphenylyl (2R,3S)-2-fluoro-3-methylpentanoate ( 12-8 ) are presented. Poly ( 12-11 )s and poly ( 12-8 )s with degrees of polymerization from 4.0 to 16.5 and poly-dispersities ≤ 1.13 have been synthesized and characterized by differential scanning cal-orimetry (DSC) and thermal optical polarized microscopy. Over the entire range of molecular weights poly ( 12-11 )s and poly ( 12-8 )s exhibit an enantiotropic SA and an unidentified SX phase. In addition, regardless of its molecular weight, poly ( 12-8 ) exhibits a S*c phase in between the SA and Sx phases. Poly ( 12-11 ) and poly ( 12-8 ) show lower transition tem-peratures and broader temperature ranges of all their mesophases as compared to the corresponding polymers without a fluorine atom on the biphenyl group. The role of the connecting group between the biphenyl and chiral group of the mesogenic unit on the phase behavior of these polymers is also discussed. Copolymers of 12-8 with (2R,3S)-2-fluoro-3-methylpentyl 4′-(11-vinyloxyundecanyloxy)biphenyl-4-carboxylate ( 13-11 ) {i.e., poly-[( 12-8 )-co-( 13-11 )] (X/Y), where X/Y represents the molar ratio of monomer 12-8 to monomer 13-11 } with DP of ca. 11 and polydispersities lower than 1.23 were also syn-thesized and characterized. Their SA and S*c mesophases exhibit continuous dependences of composition and this support the assignment of the mesophases exhibited by poly ( 12-8 ). © 1995 John Wiley & Sons, Inc.  相似文献   

16.
Two random copolyesters of poly[(R,S)-3-hydroxybutyrate-co-L-lactide] (P[(R,S)-3HB-co-LA]), prepared by equimolar reaction of (R,S)-beta-butyrolactone with L-lactic acid and (R,S)-3-hydroxybutyric acid with L-lactide, respectively, were characterized by electrospray ionization ion trap mass spectrometry (ESI-ITMS). Detailed studies of these copolyesters were performed by means of collision-induced dissociation (CID). The molecular architecture of individual copolyester macromolecules, including chemical structures of their end groups (hydroxyl and carboxylate), were established on the basis of their ESI mass spectra. The influence of an intermolecular transesterification reaction on the microstructure of the copolyester synthesized by equimolar reaction of (R,S)-3-hydroxybutyric acid with L-lactide was observed. The mass spectra provided information on sequence distribution and indicated that, despite the synthetic pathway applied, random P[(R,S)-3HB-co-LA] copolyesters were formed predominantly. The arrangements of comonomer structural units along the copolyester chains were evaluated by the respective ESI-MS/MS fragmentation pathways.  相似文献   

17.
Fang H  Liu M  Zeng Z 《Talanta》2006,68(3):979-986
A sensitive method for determination of ephedrine derivatives using headspace solid-phase microextraction (SPME) with a novel fiber followed by capillary electrophoresis has been developed. The co-poly(butyl methacrylate/hydroxy-terminated silicone oil) (BMA/OH-TSO) was used as stationary phases with the aid of γ-methacryloxypropyltrimethoxysilane (KH-570) as bridge in SPME using sol-gel-coating method and cross-linking technology. It has high extraction efficiency for ephedrine derivatives in comparison with commercial poly(dimethylsiloxane) and poly(acrylate)-coated fiber. The coating exhibits good thermal and solvent stability as well as long lifetime. A simple and flexible device for desorption of analytes after headspace SPME was constructed. The effect of various experimental parameters for SPME (temperature, time, pH, ionic strength, desorption solvent, etc.) were discussed. Field amplified sample injection (FASI) was applied for on-line sample concentration and a sensitivity enhancement of two orders of magnitude was achieved. Linear ranges were found to be 20-5000 ng/ml. The detection limits for (1R,2S)-ephedrine, (1R,2R)-pseudoephedrine and (1S,2S)-pseudoephedrine were 3, 5 and 5 ng/ml, respectively. Relative standard deviation (n = 6) was found to be 4.96-7.57%. The method was successfully applied to the analysis of ephedrine derivatives in human urine.  相似文献   

18.
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of narrowly dispersed molecular weight gel permeation chromatography (GPC) fractions was used to characterize random and microblock poly[(R)-3-hydroxybutyrate-co-epsilon-caprolactone] [P(HB-co-CL)] copolymers obtained via the acid-catalyzed transesterification of the corresponding homopolymers, poly([(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL). High-quality mass spectra were obtained, which made it possible to establish the nature of the polymer end groups. Besides the carboxylic termination, two other moieties were found: alcoholic and tosyl end groups. MALDI mass spectra of CL-rich samples possessed mostly tosyl end groups, while HB-rich samples possessed mostly alcoholic end groups, showing that the tosyl moiety is linked prevalently to CL terminal units. The higher resolution of electrospray ionization (ESI) mass spectra of lower molecular weight GPC fractions permitted the identification of the different oligomer species hypothesized in the assignment of the corresponding MALDI mass spectra. Partial methanolysis of these copolymers was explored as a method of producing mixed HB-CL oligomers to be utilized as new synthons, possessing a minor number of chiral centers from those obtained from hydrolysis of biotechnologically synthesized poly(hydroxyalkanoates) (PHAs).  相似文献   

19.
研究了不同烃基乙烯基亚砜接枝聚乙烯醇(PVA-RVSO,R=Me,Et,t-Bu,Ph)膜对纯SO2、N2的透过性能以及SO2/N2混合气体的分离性能.结果表明上述膜对SO2具有高的选择性.对不同烃基乙烯基亚砜接枝膜进行了比较.  相似文献   

20.
Three poly(ethylene oxide-co-ethylene sulfide)s with oxygen to sulfur ratios of 2/1, 2/2, and 1/2 were prepared by phase-transfer catalyzed polycondensations of (1) sodium sulfide and 1,2-bis (2-chloroethoxy)ethane, (2) 1,2-ethanedithiol and 1,2-bis(2-chloroethoxy)ethane, and (3) 1,2-ethanedithiol and 2-chloroethyl ether, respectively. A buffered solution with pH between the pKa of the monothiol (RSH) and the pKa2 of the dithiol (HS–R–SH), or H2S, was needed to obtain high molecular weight polymers, which suggests that nucleophiles transfer and react as monoanions rather than dianions. These poly(ethylene oxide-co-ethylene sulfide)s were oxidized completely to poly(ethylene oxide-co-ethylene sulfone)s using 3-chloroperoxybenzoic acid as oxidant. Both the final polymers and the precursors have regular sequenced structures and are semicrystalline. As expected, their glass transition temperatures and melting points increase and solubilities decrease with the decrease of ether oxygen to sulfur ratio. © 1994 John Wiley & Sons, Inc.  相似文献   

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