首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
X‐ray structure analysis was carried out in order to clarify the crystal structure and structural disorder of poly‐(p‐phenylenebenzobisthiazole). Two molecular chains pass through an oblique unit cell with parameters a = 11.60 Å, b = 3.588 Å, γ = 92.0° and the plane group p2. The angle between the phenylene and benzobisthiazole rings was estimated as 20.5°. Poly‐(p‐phenylenebenzobisthiazole) includes the disorder with respect to the molecular height, because the first and third layer lines are diffuse streak. On the ac plane, the molecular heights are disordered by 1/2 because 102, 602, and 404 reflections can be observed. On the bc plane, the molecular heights are disordered by every 1/5 because the 015 reflection can be observed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 376–382, 2000  相似文献   

2.
A perfect single crystal of nylon‐2,14 was prepared from 0.02% (w/v) 1,4‐butanediol solution by a “self‐seeding” technique and isothermal crystallization at 120 and 145 °C. The morphology and structure features were examined by transmission electron microscopy with both image and diffraction modes, atomic force microscopy, and wide‐angle X‐ray diffraction (WAXD). The nylon‐2,14 single crystal grown from 1,4‐butanediol at 145 °C inhabited a lathlike shape with a lamellar thickness of about 9 nm. Electron diffraction and WAXD data indicated that nylon‐2,14 crystallized in a triclinic system with lattice dimensions a = 0.49 nm, b = 0.51 nm, c = 2.23 nm, α = 60.4°, β = 77°, and γ = 59°. The crystal structure is different from that of nylon‐6,6 but similar to that of other members of nylon‐2Y. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1913–1918, 2002  相似文献   

3.
Poly‐(2‐ethynylpyridinum bromide) (PEPBP) having propargyl side chains was prepared by the direct polymerization of 2‐ethynylpyridine and propargyl bromide under mild reaction conditions without any initiator and catalysts. The polymerization proceeded well to give PEPBP with propargyl side chains in relatively high yields. Various spectral data for the polymer structure indicated that the conjugated polymer system having N‐propargylpyridinum substituent was formed. This ionic polymer was completely soluble in water, methanol, dimethylformamide, dimethyl sulfoxide, and N,N‐dimethylacetamide and well processable into thin homogeneous film. The photoluminescence intensity (λmax = 760 nm) of this polymer increased as the temperature was increased. At 1 KHz and room temperature, this polymer has k′ = 2.9 and σ = 7.3 × 10?10 (S/cm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3151–3158, 2001  相似文献   

4.
A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]0 = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (Mw /Mn = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000  相似文献   

5.
The occurrence of a molecular complex between poly(ethylene oxide) (PEO) and p‐dihydroxybenzene (hydroquinone) has been determined using different experimental techniques such as differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and Fourier transform infrared spectroscopy (FTIR). From DSC investigations, an ethylene oxide/hydroquinone molar ratio of 2/1 was deduced. During the heating, the molecular complex undergoes a peritectic reaction and spontaneously transforms into a liquid phase and crystalline hydroquinone (incongruent melting). A triclinic unit cell (a = 1.17 nm, b = 1.20 nm, c = 1.06 nm, α = 78°, β = 64°, γ = 115°), containing eight ethylene oxide (EO) monomers and four hydroquinone molecules, has been determined from the analysis of the X‐ray diffraction fiber patterns of stretched and spherulitic films. The PEO chains adopt a helical conformation with four monomers per turn, which is very similar to the 72 helix of the pure polymer. A crystal structure is proposed on the basis of molecular packing considerations and X‐ray diffraction intensities. It consists of a layered structure with an alternation of PEO and small molecules layers, both layers being stabilized by an array of hydrogen bonds. The morphology of PEO–HYD crystals was studied by small angle X‐ray scattering and DSC. As previously shown for the PEO–resorcinol complex, PEO–HYD samples crystallize with a lamellar thickness corresponding to fully extended or integral folded chains. The relative proportion of lamellae with different thicknesses depends on the crystallization temperature and time. Finally, the observed morphologies are discussed in terms of intermolecular interactions and chain mobility. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1197–1208, 1999  相似文献   

6.
A series of polyimides were prepared by a solution polycondensation reaction between 3‐carboxylmethylcyclopentane‐1,2,4‐tricarboxylic dianhydride and 4‐alkyloxybenzene‐1,3‐diamines in N‐methyl‐2‐pyrrolidone and chemical imidization with triethylamine and acetic anhydride. These polyimides possess great organo‐solubility, high optical transparency, and high pretilt angles. They are soluble not only in strong polar aprotic organic solvents such as N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, m‐cresol, and 1,4‐butyrolactone but also in common low‐boiling‐point solvents such as chloroform and tetrahydrofuran, and some are even soluble in acetone. They exhibit high transparency at wavelengths greater than 320 nm. They can generate pretilt angles greater than 5°, and some can even achieve pretilt angles greater than 10°. The pretilt angle of a polyimide increases with the increasing length of the alkyloxy side group. The polyimides possess glass‐transition temperatures between 180 and 230 °C and thermal decomposition temperatures (onset temperatures) of about 435 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1943–1950, 2000  相似文献   

7.
Several random and block copolynorbornenes with side chains containing terminal hydroxyl, amino, methacryloyl or ammonium groups were derived from the functional alkyl ester‐containing norbornenes by ring‐opening metathesis polymerization (ROMP). The main chain of ROMP‐type polynorbornene had a more important role for glass‐transition temperature in comparison with vinyl addition polymerization. There is little effect on glass‐transition temperature (about ?39 °C) of polynorbornenes with different length of alkyl side chain. The organosoluble copolynorbornenes with active crosslinkable methylacryloyl side chains derived from functional hydroxyl group were prepared to improve the thermal stability of poly(methyl methacrylate) [decomposition temperature (Td)10% = 325 °C in nitrogen] by forming networked AB crosslinked polymer (T = 367 °C in nitrogen). The sizes of nanometer‐scale polymeric micelles of block copolymers having hydrophobic alkyl ester and hydrophilic ammonium groups were measured in the range of 11–25 nm by scanning electron microscopy. These polymeric materials with various functional groups or amphiphilic architectures are accessible by ROMP, whose topology makes them particularly attractive for application potential such as biomedical and photoelectric materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4233–4247, 2005  相似文献   

8.
A route from naturally occurring myo‐inositol to hydroxyl‐bearing polyurethanes has been developed. The diol prepared from the bis‐acetalization of myo‐inositol with 1,1‐dimethoxycyclohexane was reacted with a rigid diisocyanate, 1,3‐bis(isocyanatomethyl)cyclohexane to afford the corresponding polyurethane, of which glass transition temperature (Tg) was quite high as 192 °C. The polyurethane contains side chains inherited from the acetal moieties of the diol monomer and was treated with trifluoroacetic acid to hydrolyze the acetal moieties and afford the target polyurethane functionalized with hydroxyl groups. The presence of many hydroxyl groups in the side chains, which can form hydrogen bonds with each other, resulted in a high Tg, 186 °C. In addition, the hydroxyl groups were reacted with isocyanates to achieve further side‐chain modifications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1358–1364  相似文献   

9.
The crystal structure of poly(dithiotriethylene adipate) has been determined through the best fitting of calculated and experimental X‐ray diffraction powder profiles. A triclinic cell was found with dimensions a = 4.942 (7) Å, b = 4.702 (2) Å, c = 20.56 (2) Å, α = 88.9 (2)°, β = 61.0 (1)°, γ = 67.8 (1)°, P‐1 space group, and one chain in the unit cell. A full extended trans conformation of the chain fitted satisfactory the experimental data, yielding to a discrepancy factor Rp = 0.073. A comparison between the crystal structures of poly(dithiotriethylene adipate) and poly (thiodiethylene adipate) is proposed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2677–2682, 2005  相似文献   

10.
Poly(δ‐valerolactone) (PVL) crystals in the form of chain‐folded lamellae were prepared by isothermal crystallization from a 2‐methylbutane‐2‐ol solution. Wide‐angle and small‐angle X‐ray diffraction data, obtained from PVL lamellae sedimented to form oriented mats, were supplemented with morphological and structural data from electron microscopy, both imaging and diffraction. The diffraction signals index on an orthorhombic unit cell with the parameters a = 0.747 ± 0.002 nm, b = 0.502 ± 0.002 nm, and c (chain axis) = 0.742 ± 0.002 nm. Similar unit cell parameters were obtained from crystals grown from 1‐octanol and also from drawn melt‐pressed films. The evidence supports a model containing two antiparallel chain segments in the unit cell. The c value of 0.742 nm is appropriate for an all‐trans or onefold helical backbone conformation for the straight stems. Possible slight perturbations at the ester units from the all‐trans backbone conformation are discussed. Computerized modeling was used to optimize the adjacent‐reentry folded structure. The setting angles, with respect to the a axis, are ±58° for the corner and center chains. The lamellae are 7.26 ± 0.05 nm thick, and the chains run orthogonal to the lamellar surface. The chains fold in the diagonal (110) and (11¯0) planes in an alternating fashion. The X‐ray diffraction data suggest that a proportion of adjacent paired antiparallel entities, or hairpin units, are c‐axis‐sheared, and a relationship to the results obtained from drawn films is discussed. A brief comparison is also made with related polymer structures. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2622–2634, 2001  相似文献   

11.
A doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethyl methacrylate)‐b‐Poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) (PDMAEMA‐b‐PEG‐b‐PDMAEMA) with well‐defined structure and narrow molecular weight distribution (Mw/Mn = 1.21) was synthesized in aqueous medium via atom transfer radical polymerization (ATRP) of N,N‐dimethylamino‐2‐ethylmethacrylate (DMAEMA) initiated by the PEG macroinitiator. The macroinitiator and triblock copolymer were characterized with 1H NMR and gel permeation chromatography (GPC). Fluorescence spectroscopy, dynamic light scattering (DSL), transmittance measurement, and rheological characterization were applied to investigate pH‐ and temperature‐induced micellization in the dilute solution of 1 mg/mL when pH > 13 and gelation in the concentrated solution of 25 wt % at pH = 14 and temperatures beyond 80 °C. The unimer of Rh = 3.7 ± 0.8 nm coexisted with micelle of Rh = 45.6 ± 6.5 nm at pH 14. Phase separation occurred in dilute aqueous solution of the triblock copolymer of 1 mg/mL at about 50 °C. Large aggregates with Rh = 300–450 nm were formed after phase separation, which became even larger as Rh = 750–1000 nm with increasing temperature. The gelation temperature determined by rheology measurement was about 80 °C at pH 14 for the 25 wt % aqueous solution of the triblock copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5869–5878, 2008  相似文献   

12.
A series of side‐chain liquid‐crystal polymers, poly[6‐[4‐(4′‐n‐alkyl benzoateazo)phenoxy]‐hexylmethacrylate]s (PMAzoCOORm, m = 1, 2, 3, 4, 5, 6, 8, 10, 14, and 18) have been prepared by two synthetic methods. The chemical structure of the monomers was confirmed by 1H NMR and mass spectrometry. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatograph. The phase behaviors of polymers were investigated by the combination of techniques including differential scanning calorimetry, polarized optical microscopy, and small‐angle X‐ray scattering. For m = 1, 2, 3, 4, 5, and 6, the polymers exhibited a monosmectic A phase in which the smectic layer period was almost identical to the side‐chain length. In addition, for m = 2, 3, 4, and 5, they presented the monosmectic C phase in low temperature; moreover, the tilt angle increased from 23.3 to 40.5°. For m = 8, 10, 14, and 18, the polymers showed a bilayer smectic A phase in which the layer spacing was larger than a fully extended side chain but less than two extended chains. On the other hand, for the clearing point, with the increasing of m, it first decreased, and then increased. All of these indicated that the length of alkyl tails played an important role in the phase behaviors of these polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2759–2768  相似文献   

13.
The present report describes the synthesis of a densely grafted copolymer consisting of a rigid main chain and flexible side chains by the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from an ATRP initiator‐bearing poly(phenylacetylene) [poly(BrPA)]. Poly(BrPA) was obtained by the polymerization of 4‐ethynylbenzyl‐2‐bromoisobutyrate using [Rh(NBD)Cl]2 in the presence of Et3N. The 1H NMR spectrum showed that poly(BrPA) was in the cis‐transoid form. Upon heating at 30 °C for 24 h the cis‐transoid form was maintained. ATRP of MMA from the poly(BrPA) was carried out at 30 °C using CuX (X = Br, Cl) as the catalyst and N,N,N′,N′,N′‐pentamethyldiethylenetriamine as the ligand, and the resulting graft copolymers were investigated with 1H NMR and SEC. To analyze the graft structure in more detail, the graft copolymers were hydrolyzed with KOH and the resultant poly(MMA) part was investigated with 1H NMR and SEC. The polydispersity indexes of 1.25–1.45 indicated that the graft copolymers have well‐controlled side chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6697–6707, 2006  相似文献   

14.
Poly(acryloyl‐L ‐proline‐methyl ester) ( 1 ) has optically active side chain, and constitutes thermoresponsive hydrogels upon crosslinking. In this study, we have prepared uncrosslinked polymer of 1 with a 10‐kGy irradiation dose of γ‐ray. For this polymer, 1 , variable temperature circular dichroism (CD) and 1H NMR spectra have been studied in the range of 0–30 °C. The intense CD spectrum at 0 °C suggests that the side chains in 1 have an ordered orientation. The CD intensity decreases gradually with increasing temperature. The decreased intensity of CD spectra indicates that the disordering occurs for the side‐chain orientation. The CD band shape changes discontinuously at 20 °C. In the 1H NMR spectra, signals disappear above 20 °C. These spectral change at 20 °C indicate that the phase transition occurs at around 20 °C from swollen to shrunken phase. Even after the phase transition, the CD spectra are still changing with isochromic point at 212 nm. It appears that the side‐chain conformation is still changing from one state to the other state in the shrunken phase polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4524–4530, 2000  相似文献   

15.
The crystal structure of poly(ω‐pentadecalactone) (PPDL) synthesized by enzyme‐catalyzed polymerization was determined by full‐profile refinement. A pseudo‐orthorombic monoclinic unit cell with dimensions a = 7.49(1), b = 5.034(9), and c = 20.00(4)Å (fiber axis), and α = 90.06(4)° hosts two monomeric units belonging to polymer chains with opposite orientation, according to the P21 space‐group symmetry. A close similarity to the crystal structure of poly(?‐caprolactone) was evident. However, the even number of backbone atoms in the monomer unit of PPDL leads to a lower crystal symmetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1009–1013, 2003  相似文献   

16.
Phase equilibrium studies for semiconcentrated solutions of rodlike poly(γ‐benzyl L ‐glutamate) having oligo(ethylene glycol) as side chains (PBLG‐g‐OEG) have been investigated. The phase‐boundary concentrations in isotropic and anisotropic phases for N,N‐dimethylformamide (DMF) solution of PBLG‐g‐OEG with short side chains (PBLG2‐g‐380) are higher than those for solution of PBLG‐g‐OEG with long side chains (PBLG2‐g‐770). The lattice theory and the scaled particle theory for nematic solution, which don't distinguish the molecular architecture of the rodlike polymer, cannot explain this experimental result. Repulsive interaction between rodlike polymers by means of the attached side chains is proposed for the molecular orientation of PBLG‐g‐OEG in anisotropic state in order to describe the experimental result. Ternary phase diagrams of PBLG‐g‐OEG/poly(ethylene glycol) (PEG)/DMF show that the miscibility of rodlike PBLG‐g‐OEG and coiled PEG is most enhanced in the system of PBLG2‐g‐770, which has longest and largest amount of side chains. This experimental observation is explained by using the calculation based on the lattice theory and the repulsive interaction of side chains proposed above. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1331–1340, 2000  相似文献   

17.
Poly(dipentylsilylene) copolymers containing n‐pentyl‐n‐oct‐7‐enylsilane units were prepared by reductive coupling of the corresponding dichlorosilanes. Linear high molecular weight and some crosslinked polymer were obtained. The soluble products exhibited optical and thermal properties like poly(dipentylsilylene). Differential scanning calorimetry was used to investigate crystallization and to monitor thermal crosslinking. Vinyl functionalized side chains were hydrosilylated with dipentylsilane and dimethylchlorosilane and crosslinked via the side chains. Hydrosilylation with di‐n‐pentyl(trimethylsiloxypropyl)silane led to a partial hydroxy functionalization of the polysilylene and enabled anionic PEO grafting of the poly(dipentylsilylene). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2306–2318, 2000  相似文献   

18.
We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d8 together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837  相似文献   

19.
A series of new polyimides containing alicyclic units and alkyloxy side chains were prepared from 9,10‐dialkyloxy‐1,2,3,4,5,6,7,8‐octahydro‐2,3,6,7‐anthracenetetracarboxylic 2,3:6,7‐dianhydrides and various aromatic diamines. Their physical properties and structures were investigated. Polymers were obtained with inherent viscosities of 0.24–0.53 dL/g. In comparison with the aromatic polyimides, most polymers were readily soluble in common organic solvent such as N‐methylpyrrolidone and m‐cresol. These polymers had glass‐transition temperatures between 111 and 296 °C depending on the structure of the repeating unit and 10% weight‐loss temperatures of 418–477 °C in nitrogen. Wide‐angle X‐ray diffractometry for as‐polymerized samples revealed very low crystallinity and layered structures, which were better developed in the polymers with longer side chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1764–1774, 2002  相似文献   

20.
A novel complex [Cu(NnpPy)2(HlTCB)(H1O)]·2H2O (NITpPy = 2‐(pyrid‐4′‐yl)‐4,4,5,5‐tetramethyl‐1, 3‐dioxoimidazoline; H2TCB = 1, 5‐dicarboxybenzene carboxylic‐2, 4‐diacid) has been synthesized and characterized by X‐ray crystallography analysis. The crystal structure consists of infinite chains of Cu‐(NITpPy)2(H2O) units linked by H2TCB ligands. The complex crystallizes in triclinic system with space group PI. Crystal data: a = 1.0594(2) nm, b = 1.3830(3) nm, c = 1.5551(3) nm, a = 67.75(3)°, β = 89.83(3)°, γ = 70.54(3)°. The variable magnetic susceptibility studies lead to magnetic coupling constant values of J1= ?11.18 cm‐1 (Cu—Rad) and J2 = ?4.06 cm?1 (Cu—Cu).  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号