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1.
Polymer miscibility has been discovered in a blend system comprising poly(ether imide) (PEI) and a new poly(ether diphenyl
ether ketone) (PEDEK). The miscibility of the PEDEK/PEI polymer system (quenched from the molten state) was investigated in
this study using differential scanning calorimetry and Fourier transform (FT-IR) spectroscopy. A composition-dependent single
glass-transition temperature (T
g) in the PEDEK/PEI blends over a full composition range was observed; the sharp transition width and the T
g–composition relationship both suggest that the scale of mixing is fine and uniform. Evidence based on observation of the
cold-crystallization peak and suppression of the blend crystallinity and melting peak also indicated intimate intermolecular
mixing. The FT-IR result yielded further evidence that the physical interactions leading to miscibility were weak, with no
apparent specific interactions between the constituent polymers. Relationships between structures and interactions responsible
for the miscibility in PEI and several ether-ketone-type polymers are briefly discussed.
Received: 8 July 1999 Accepted in revised form: 21 October 1999 相似文献
2.
A series of proposed plasticizers for poly(vinyl chloride) (PVC), based on poly(?-caprolactone) (PCL) with octanoate and benzoate-terminal groups, were synthesized with various microstructures and molecular weights (MW) and tested for biodegradability as well as for mechanical performance, and leaching resistance in blends with PVC. The plasticization efficiency of each was characterized by measuring the glass transition temperature (Tg) and tensile properties of PCL/PVC blends. The PCL-octanoate plasticizers demonstrated plasticization efficiency similar to di(ethylhexyl) phthalate (DEHP) with the same plasticizer loading. PCL-benzoate/PVC blends had much higher Tgs (∼20 °C higher) compared to PCL-octanoate/PVC and DEHP/PVC blends. Yield stresses were about two times higher for PCL-benzoate/PVC blends compared to PCL-octanoate/PVC and DEHP/PVC blends, reflecting the stiffer nature of such blends. Biodegradation was rapid for all PCL-octanoates, with the exception of linear PCL-octanoates with arm molecular weights >103 g mol−1. Biodegradation rates of PCLs by Rhodococcus rhodocrous were not affected by microstructure for the range of PCL topologies studied (linear versus three or four arms) but were slower for PCLs made from commercial PCL-diols that had a central ether linkage due to the initiator used to make these compounds. Leaching resistance was higher as PCL molecular weight increased and, for pairs of comparable sized species, significantly less PCL-benzoate leached out compared to the PCL-octanoate. For the range of PCL topologies studied, the number of arms did not significantly affect leaching resistance. In summary, both the end group and the molecular weight influenced the leaching resistance of the PCL. PCL-octanoates were comparable plasticizers to DEHP in terms of the mechanical properties examined, and were rapidly degraded by a common soil microorganism. 相似文献
3.
Huan Wang Baoqing Shentu Wenli Zhang Cheng Gu Zhixue Weng 《European Polymer Journal》2012,48(7):1205-1211
Poly(amindoamine) (PAMAM) was grafted onto magnetic Fe3O4 nanoparticles to produce PAMAM grafted Fe3O4 (shortened as Mag-PAMAM). Mag-PAMAM coordinated with Cu(II) to form the supported Cu(II)–PAMAM complex (shortened as Cu(II)/Mag-PAMAM). The stoichiometric ratio between amine groups in Mag-PAMAM and Cu(II) was found to be 4. The Cu(II)/Mag-PAMAM complexes were employed to catalyze the oxidative polymerization of 2,6-dimethylphenol (DMP) in water. The Cu(II)/Mag-PAMAM complexes demonstrated the excellent selectivity of C–O/C–C coupling and reactivity to form poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). After polymerization, the Cu(II)/Mag-PAMAM complexes were recovered by an external magnetic field and used repeatedly in the next run with additional Mag-PAMAM and copper ions. After three runs of oxidative polymerization of DMP, the recovery ratio of the catalyst was about 95% and the yield of PPO maintained a relatively high value. 相似文献
4.
Hiraishi T Masuda E Miyamoto D Kanayama N Abe H Maeda M 《Macromolecular bioscience》2011,11(2):187-191
We recently discovered that poly(aspartate) (PAA) hydrolase‐1 from Pedobacter sp. KP‐2 has a unique property of specifically cleaving the amide bond between β‐aspartate units in thermally synthesized PAA (tPAA). In the present study, the enzymatic synthesis of poly(α‐ethyl β‐aspartate) (β‐PAA) was performed by taking advantage of the substrate specificity of PAA hydrolase‐1. No polymerization of diethyl L ‐aspartate by native PAA hydrolase‐1 occurred because of the low dispersibility of the enzyme in organic solvent. Poly(ethylene glycol) (PEG) modification of the enzyme improved its dispersibility and enabled it to polymerize the monomer substrate. MALDI‐TOF MS analysis showed that the synthesized polymer was observed in the range of m/z = 750–2 500. This analysis also revealed that the polymer was composed of ethyl aspartate units, containing either an ethyl ester or a free carboxyl end group at its carboxyl terminus. 1H NMR analysis demonstrated that the synthesized polymer consisted of only β‐amide linkages. Thus, the present results indicate that PAA hydrolase‐1 modified with PEG is useful for the synthesis of β‐PAA due to its unique substrate specificity and good dispersibility in organic solvent.
5.
R. S. Vartapetian E. V. Khozina J. Kärger D. Geschke F. Rittig M. M. Feldstein A. E. Chalykh 《Colloid and polymer science》2001,279(6):532-538
We have applied the PFG NMR technique to investigate the translational mobility in the PVP-PEG system as a function of composition
and temperature at the stages of PVP-PEG complex formation, its swelling, and dissolution in excess of liquid PEG. It has
been found that the variations of the spin-echo attenuation with PEG content, water amount, and temperature reflect the different
stages. The first two stages are characterized by a distribution of the self-diffusion coefficients of PEG involved in the
network. The dissolution shows two diffusion coefficients; the fast one is attributed to PEG molecules, the slow one to the
associates of PEG and PVP. The temperature dependencies can be described by an Arrhenius law with an activation energy depending
on the composition of the blend. The concentration dependence of the PEG self-diffusion coefficients in the blend occurred
to be independent of the molecular weight of PVP. The results are discussed in terms of the Mackie-Meares model.
Received: 23 August 2000 Accepted: 19 October 2000 相似文献
6.
Synthesis and application of 2-amino-3-(α-N-phenylmethyl-2′-amino-1′,4′-naphthoquinonyl)-1,4 naphthoquinone (S) as a neutral ionophore for the determination of gallium(III) in PVC-based membrane sensors has been described. The sensor based on membrane composition (w/w, mg%); 5.0 (S):30.0 (PVC):5.0 (KTpClPB):60.0 (o-NPOE) is the best and showed a working range of 2.3 × 10−7 to 1.0 × 10−2 M with detection limit of 1.2 × 10−7 M. It can tolerate non-aqueous media up to 15% with a slope of 19.7 mV decade−1 of activity. The sensor has been used to assess the Ga(III) concentration in different natural samples (peach and tomato leaves, coal-fly-ash and river sediments). It can be used for 2.5 months without any distortion in results, after which, leaching of ionophore was observed from the membrane phase. The proposed sensor has shown a good dynamic response time of 11 s. 相似文献
7.
Giovanni Maglio Rosario Palumbo Giovanni Pietro Rachiero Maria Carmela Vignola 《Macromolecular bioscience》2002,2(6):293-297
Segmented poly(ether-ester-amide)s, (PEEA)s, of controlled hydrophilicity degree, based on poly(ε-caprolactone) (PCL), were synthesized according to a facile two-step procedure using α,ω-dihydroxy oligomeric PCL, 4,7,10-trioxa-1,13-tridecanediamine and macromers prepared from poly(ethylene glycol)s and adipoyl chloride. The PEEAs showed M n values in the range 5–11.5 kDa. A PCL-type crystallinity was found by WAXS. DSC indicated Tm values (49–51 °C) close to that of PCL macromer. Single glass transitions were observed both by DSC and DMTA techniques and the Tg values (−58–−50 °C by DSC) were slightly higher than that of PCL. The water uptake was in the range 4.8–26.0 wt.-% depending on the length of the poly(ethylene glycol) segment.
8.
《Computational and Theoretical Polymer Science》2000,10(3-4):371-381
Molecular dynamics calculations of an amorphous interfacial system of poly(methyl methacrylate) (PMMA) and poly(tetrafluoroethylene) (PTFE) containing about 10,000 interaction sites were performed for 15 ns under constant pressure and constant temperature conditions. The time evolutions of the thickness, density and number of atomic pairs in the interfaces suggested that the interfaces reached their equilibrium states with an interfacial thickness of about 2 nm at 500 K. The molecular motion in the interface and bulk was compared using mean square displacement and torsional autocorrelation function. The separation at a PMMA/PTFE interface was mimicked using non-equilibrium molecular dynamics calculations by applying the potential energy to the MD cell in a direction perpendicular to the interface. Initially, the PTFE layer close to the interface was deformed, and before complete separation, some segments of the PTFE molecules extended from the bulk to the surface of the PMMA layer, which were attached by the intermolecular interaction. The remaining PTFE molecules were entangled in the bulk, which probably prevented the transfer of the PTFE molecules to the surfaces of the PMMA layers. On the other hand, the PMMA layer was only slightly deformed. This separation behavior can be explained by taking into account the intermolecular interaction, the barrier to the conformational changes of the backbones and the entanglement of the PTFE molecules in the bulk. 相似文献
9.
10.
Maurizio Penco Luciana Sartore Fabio Bignotti Mariapia Rossini Alberto D'Amore Federica Fassio 《Macromolecular Symposia》2002,180(1):9-22
Binary blends based on poly(vinyl chloride) (PVC) were prepared both by casting from tetrahydrofuran (THF) and by mixing in the melt form, in a discontinuous mixer, PVC and multi-block copolymers containing poly(ϵ-caprolactone) (PCDT) and poly(ethylene glycol) (PEG) segments. PCDT-PEG copolymers were synthesized using a polycondensation reaction where the α,ω-bis-chloroformate of an oligomeric poly(ϵ-caprolactone) diol terminated (PCDT) and oligomeric PEG were employed as macromonomers. For comparison purposes, blends PVC with starting oligomers as well as with mixtures containing a typical low molecular plasticizer, dioctylphthalate (DOP), were also prepared. The copolymer miscibility was studied by differential scanning calorimetry (DSC) and FT-IR spectroscopy. The blend morphology was investigated by polarized light microscopy (PLM). A higher miscibility with PVC was observed for copolymers compared to PEG. 相似文献
11.
Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-b-PEG-b-CL) and poly(DTC-b-CL-b-DTC) 总被引:2,自引:1,他引:1
CHEN Wei LING Jun & SHEN Zhiquan Institute of Polymer Science Zhejiang University Hangzhou China 《中国科学B辑(英文版)》2005,48(4)
PCL possesses a wide range of medical applications, such as tissue engineering and controlled drug release, because of its good biodegradability and miscibility. In order to extend the use of PCL, researchers have been exploring its structural and chemica… 相似文献
12.
The solubility of naphthalene was investigated in aqueous solutions of triblock copolymers poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PEG–PPG–PEG) and (2-hydroxypropyl)cyclodextrins. The results with solutions of the individual solubilizers were as expected: the solubility enhancement was much higher with a micelle-forming copolymer than with the non-micellizing one and with (2-hydroxypropyl)--cyclodextrin (HPBCD) than with (2-hydroxypropyl)--cyclodextrin (HPACD). Although the formation of inclusion complexes between HPACD and PEG and between HPBCD and PPG is well established, the naphthalene solubility in mixed solutions does not significantly deviate from that predicted for a mixture of independent solubilizers. Thus the interactions between HPCD and PEG–PPG–PEG copolymers are not strong enough to disrupt micelles and aggregates formed by those copolymers. In fact, slight synergetic deviations were observed with the micellizing copolymer, indicating the existence of ternary naphthalene/HPCD/copolymer interactions. For pharmaceutical applications, it is important that the solubilization efficacy of PEG–PPG–PEG copolymers and that of cyclodextrins modified by the 2-hydroxypropyl group would not be compromised if these two types of solubilizers were co-administered. 相似文献
13.
Fabio Bignotti Maurizio Penco Luciana Sartore Salvatore D'Antone Alberto D'Amore Gloria Spagnoli 《Macromolecular Symposia》2002,180(1):257-266
Thermodegradative investigations of two classes of multi-block copolymers containing poly(D,L-lactic-glycolic acid) (PLGA) and either poly(ethylene glycol) (PEG) or poly(ϵ-caprolactone) diol-terminated (PCDT) segments were performed. In particular, the influence of the type and length of the segments as well as of the molar ratio between the D,L-lactic acid (LA) and glycolic acid (GA) residues was investigated at 180°C in air by viscometry, FT-IR analysis and isothermal thermogravimetry. The thermal oxidative degradation of these materials is largely affected by the LA/GA ratio, a higher LA content generally imparting higher stability. The FT-IR analysis suggests that, depending on the composition of the PLGA segments, degradative processes are triggered which can lead to a preferential degradation of the blocks. 相似文献
14.
Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical
structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock
copolymer leads to lower T
g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron
microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic
fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin
were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4%
and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs. 相似文献
15.
The appearance of an endothermic annealing peak in semicrystalline poly(phenylene sulphide) and semicrystalline poly(ethylene
terephthalate) after annealing at or above the cold-crystallization temperature is investigated by temperature-modulated differential
scanning calorimetry, thermo-mechanical analysis and dynamic-mechanical analysis. The results indicate relaxation processes
in the interlamellar amorphous phase, which is in a strongly constrained state after cold crystallization. During the annealing
treatments rearranging processes take place. These processes result in a separation of the amorphous phase into an interlamellar
relaxed and a “pseudo-crystalline” phase.
Received: 27 October 1998 Accepted in revised form: 19 January 1999 相似文献
16.
New hydrogels based on polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) of different degrees of hydrolysis were synthesized. To form the network the PEG was modified at their ends with acyl chloride groups to be used as the crosslinking agent. The compositions of the hydrogels were between 50% and 90% by weight of PEG and PVA of various degrees of hydrolysis were used. It was found that the degree of hydrolysis of the PVA and the PEG content influence the equilibrium water content of the hydrogel. The process of swelling of all the hydrogels prepared followed a second-order kinetics. 相似文献
17.
B. Mayer Ch.Th. Klein I.N. Topchieva G. Köhler 《Journal of computer-aided molecular design》1999,13(4):373-383
This paper presents a computational study on the formation of a molecular necklace formed by specific threading of cyclodextrins (CDs) on block copolymers. Structural as well as energetic principles for the selective complexation of - and -cyclodextrin with poly(ethylene oxide)–poly(propylene oxide) block copolymers (PEO–PPO) are elucidated considering a diblock copolymer of equimolecular composition (PEO)4–(PPO)4 as guest. A non-statistical distribution of CDs, i.e. -CDs primarily located on the PEO chain and -CDs on PPO blocks of the polymer, is based on a variety of structural features and energetic preferences considering both potential as well as solvation energies. This selectivity becomes already obvious considering 1:1 complexes between PEO and PPO monomers and the two CDs, but is increasingly evident when calculating higher order ensembles. Besides the host–guest interaction, docking between CDs themselves is an important, also non-statistical, prerequisite for the self-assembly of highly ordered tubes. The formation of intermolecular hydrogen bonds between adjacent CDs in a tubular aggregate gives an important contribution to the overall stability of the molecular necklace. The net effect, based on the preferential interaction between host and guest as well as between the host molecules themselves, results in the formation of a stable, highly ordered macromolecular, multicomponent aggregate. 相似文献
18.
A series of triblock copolymers composed of poly(ethylene glycol) (PEG) and poly(β-amino ester urethane) (PAEU) was synthesized and characterized. Its aqueous solution can be used as a non-cytotoxic, biodegradable, and pH/temperature-sensitive hydrogel system. The copolymer solutions exhibited sol-to-gel and gel-to-sol transitions with increasing pH and temperature, respectively. The properties of this hydrogel system, such as its sol–gel transition diagram, mechanical properties, and degradation rate, can be controlled by modulating the PEG molecular weight, PAEU block length, copolymer concentration, or structure of the monomers. The presence of urethane groups and ionized tertiary amine groups in the copolymer solution at lightly acidic pH may lead to a strong interaction of the copolymer with formulated bioactive therapeutic agents, while the existence of the gel state under physiological conditions (37 °C, pH 7.4) may enable this copolymer hydrogel to be applicable as a drug/protein carrier. 相似文献
19.
Petr Svoboda Dagmar Svobodova Dagmar Merinska Toshiaki Ougizawa 《European Polymer Journal》2009,45(8):2434-2442
A blend of poly(ε-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) containing 27.5 wt% of acrylonitrile having the critical composition (80/20 PCL/SAN) was studied. This PCL/SAN blend having a lower critical solution temperature (LCST) phase boundary at 122 °C offered an excellent opportunity to investigate, firstly the kinetics of phase separation above LCST (125-180 °C), and secondly the kinetics of phase dissolution below LCST (50-115 °C). The blend underwent a temperature-jump above LCST where spinodal decomposition (SD) proceeded, yielding a regularly phase-separated structure (SD structure). Then, it was quenched to the temperatures below LCST when the phase dissolution proceeded. Optical microscopy was used to observe the spinodal decomposition qualitatively while light scattering was used to characterize the phase separation and phase dissolution quantitatively. It was found that during phase dissolution the peak maximum moved towards a smaller angle (wavelength of concentration fluctuations increased) while the peak intensity decreased. This behavior was explained by a model. Also it was found that the fastest phase dissolution kinetics at 80 °C, which was characterized by an apparent diffusion coefficient, was about 10 times slower than the kinetics of phase separation at 180 °C. 相似文献
20.
The enzymatic hydrolysis by Humicola lanuginosa lipase (HLL) of spread insoluble monolayers of poly (α-hydroxy acid)s with various molecular weights and various lactic–glycolic
molar ratios was studied using a barostat surface balance. The interfacial hydrolysis under enzyme action leads to the progressive
fragmentation of the polymer molecules. The appearance at the interface of charged insoluble fragments was detected by measuring
the surface potential, while the solubilization of the small soluble fragments was detected by measuring the decrease in the
surface area. The data obtained were used to test the mode of fragmentation: either random or chain-end scission. The catalytic
specific activity of HLL was estimated in the framework of the random scission model and compared with the activities obtained
for the hydrolysis of simple molecules of di- and tri-glycerides organized as monolayers or emulsion.
Received: 9 August 1999 Accepted: 4 January 2000 相似文献