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1.
Solution thermodynamics of PEG samples in aqueous and nonaqueous (methanol, chloroform, tetrahydrofuran, and dimethylsulfoxide) solutions have been investigated by viscometric studies at 25, 30, 35, and 40°C. The hydrodynamic expansion factor, ah, and the unperturbed root mean square end‐to‐end distance, , found for the system indicated that the polymer coils contract as the temperature is raised. The long‐range interaction parameter, B, was also evaluated and a significant decrease with increasing temperature was observed. The theta temperatures, θ, obtained from the temperature dependence of (1/2 ? χ) and the second virial coefficient, A2, are quite good in agreement with the calculated values evaluated via extrapolation and interpolation methods. The thermodynamic interaction parameter, χ, was evaluated through the sum of the individual values of enthalpy and entropy dilution parameters for PEG samples. The restrictions applying to the establishment of concentration regimes, short‐range, and long‐range interactions are discussed. A parallelism is found between solubility profiles obtained by solution viscometry and solubility parameter approaches for PEG/solvent systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

2.
This work was committed to the polymerization of hydrophobic ketoethyl methacrylate monomer in aqueous medium in the presence of cyclodextrin, instead of polymerizing the monomer in toxic and volatile organic solvents. For this purpose, a new ketoethyl methacrylate monomer, p‐methylphenacylmethacrylate (MPMA), was synthesized from the reaction of p‐methylphenacylbromide with sodium methacrylate in the presence of triethylbenzylammonium chloride. The monomer was identified with FTIR, 1H and 13C‐NMR spectroscopies. Hydroxypropyl‐β‐cyclodextrin (HPCD) was used to form a water‐soluble host/guest inclusion complex (MPMA/HPCD) with the hydrophobic monomer. The complex was identified with FTIR and NMR techniques and polymerized in aqueous medium using potassium persulfate as initiator. During polymerization the resulting hydrophobic methacrylate polymer precipitated out with a majority of HPCD left in solution and a minority of HPCD bonded on the resulting polymer. The thus‐prepared polymer exhibited little difference from the counterparts obtained in organic solvent in number average molecular weight (Mn), polydispersity (Mw/Mn) and yield. The investigation provides a novel strategy for preparing hydrophobic ketoethyl methacrylate polymer in aqueous medium by using a monomer/HPCD inclusion complex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

3.
Poly(ethylene glycol)‐block‐poly(N‐isopropylacrylamide) (PEG‐b‐PNIPAM) block copolymers were synthesized by atom transfer radical polymerization, and the α‐cyclodextrin (α‐CD) induced self‐assembly characteristics of the system were elucidated. Below the lower critical solution temperature (LCST) of PNIPAM, CD threaded onto the PEG segments and induced micellization to form rod‐shaped nanostructures comprising of a PEG/α‐CD condensed phase and a PNIPAM shell. Increasing the temperature of system above the LCST caused the PNIPAM segments to collapse, which resulted in the dethreading of the CD. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

4.
The mass transfer properties of mono‐ and ditopic β‐cyclodextrin‐based receptors have been evaluated in a biphasic palladium‐catalyzed Tsuji–Trost reaction and compared to one of the best mass‐transfer promoters, namely the randomly methylated β‐cyclodextrin. While monotopic receptors appeared to be poor mass‐transfer promoters of long alkyl chain allyl carbonates or urethanes, cooperative effects have been evidenced with ditopic cyclodextrin‐based receptors, opening new perspectives in aqueous organometallic catalysis.  相似文献   

5.
A copolymer prepared by the copolymerization of ethyl vinyl ether and maleic anhydride underwent amidoacidation with N,N‐dimethylaminopropylamine. The obtained ethyl vinyl ether/dimethylaminopropyl maleamidic acid copolymer was then reacted with methyl iodide to yield poly(methyl iodide quaternized ethyl vinyl ether/N,N′‐dimethylaminopropyl maleamidic acid) (MIQEDMAPMA). The greatest difference from other polyelectrolytes was the carboxylic group on the polymer chain unit of MIQEDMAPMA. Its aqueous solution properties in various salts and at various pH values were studied by measurements of the reduced viscosity and intrinsic viscosity. The reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the types and concentrations of the added salts. The tendency of the salt effect was similar to that of other polyelectrolytes; that is, soft salt anions were more easily bound to the quaternary ammonium (R4N+) of MIQEDMAPMA than hard salt anions. Some salt ions strongly attracted the quaternary ammonium of the cationic polymeric side chain for the agglomeration of the polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2261–2269, 2003  相似文献   

6.
For the increasing demands of multifunctional materials in applications such as drug delivery system, a pH‐ and temperature‐responsive polyelectrolyte copolymer gel system was studied using rheometry. Rheological properties, determined by plate–plate rheometry in oscillatory shear, of hydrogels formed by free radical initiated copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) in the presence of methylene bisacrylamide (MBAA) as crosslinker are compared with the properties of semi‐interpenetrating network (SIPN) polyelectrolyte gels made by incorporation of poly(ethylene glycol) with molar mass 6000 g mol?1 (PEG6000). Based on our systematic studies for this PEG/SIPN system, the effects of initiator and crosslinker concentration, relative proportions of comonomer units in the main chains, PEG6000 content and temperature on viscoelastic properties, unusual high storage moduli at small strain for the SIPN were discussed. The SIPN gel with characteristics of PEG molecules as well as pH and temperature responsiveness from AMPS and NIPA units has potential application in drug delivery system design. Ice‐like rheological behavior of the PEG/AMPS‐NIPA SIPN gels at low temperature was first time reported and water remains homogeneous without phase separation in PEG/AMPS‐NIPA SIPN hydrogels at low temperature may be considered as an ideal candidate for water storage material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

7.
To improve the mechanical strength of natural hydrogels and to obtain a sustained drug‐delivery device, temperature‐/pH‐sensitive hydrogel beads composed of calcium alginate (Ca‐alginate) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared in the presence of poly(sodium acrylate) (PAANa) with ultrahigh molecular weight (Mη ≥ 1.0 × 107) as a strengthening agent. The influence of PAANa content on the properties, including the beads stability, swelling, and drug‐release behaviors, of the hydrogels was evaluated. Scanning electron microscopy and oscillation experiments were used to analyze the structure and mechanical stability of the hydrogel beads, respectively. The results show that stability of the obtained Ca‐alginate/PNIPAAm hydrogel beads strengthened by PAANa the alginate/poly(N‐isopropyl acrylamide) hydrogel bead (SANBs) was significantly improved compared to that of the beads without PAANa (NANBs) at pH 7.4. The swelling behavior and drug‐release capability of the SANBs were markedly dependent on the PAANa content and on the environmental temperature and pH. The bead sample with a higher percentage of PAANa exhibited a lower swelling rate and slower drug release. The drug release profiles from SANBs were further studied in simulated intestinal fluid, and the results demonstrated here suggest that SANBs could serve as a potential candidate for controlled drug delivery in vivo. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

8.
The thermoresponsive properties in aqueous solution of the graft copolymer poly(acrylic acid‐co‐2‐acrylamido‐2‐methyl propane sulfonic acid)‐g‐poly(N‐isopropylacrylamide) [P(AA‐co‐AMPSA)‐g‐PNIPAM] were studied and compared to the corresponding behavior of the poly(acrylic acid)‐g‐poly(N‐isopropylacrylamide) (PAA‐g‐PNIPAM) graft product. Both products contain about 40% (w/w) of PNIPAM, whereas the backbone, P(AA‐co‐AMPSA), of the first copolymer contains about 40% of AMPSA mole units. The strongly charged P(AA‐co‐AMPSA)‐g‐PNIPAM graft copolymer was water soluble over the whole pH range, whereas the PAA‐g‐PNIPAM copolymer precipitated out from water at pH < 4. As a result, the first product exhibited a temperature‐sensitive behavior in a wide pH range, extended in the acidic region, whereas in semidilute aqueous solutions, an important thermothickening behavior was observed, even at low pH (pH = 3.0). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3466–3470, 2004  相似文献   

9.
A hydrogel is a polymeric material that exhibits the ability to swell in water and retains a significant fraction of water within its structure, but does not dissolve in water. One of the major problems in the application of these materials is their relatively poor mechanical strength, attributed to the high degree of hydration of the gel. This work was directed to the study of the interactions between hydrophobic and hydrophilized fibers, with the objective of optimization of the mechanical properties of poly(N‐vinyl‐2‐pyrrolidone) membranes. The membranes were prepared by electron‐beam irradiation of an aqueous polymer solution. A nonwoven cloth made of polypropylene matted fiber, grafted with methyl methacrylate, was employed as a reinforcement. The changes in the main properties of the membranes, such as the gel content, swelling characteristics, cytotoxicity, and mechanical behavior, were investigated. The results showed an increase of 800% in tensile strength, without changes in the swelling and cytotoxicity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 662–666, 2002  相似文献   

10.
A kind of polyacrylamide (PAM) latex product dispersed in an aqueous solution was successfully prepared through the aqueous two‐phase polymerization of acrylamide in an aqueous solution of poly(ethylene glycol) (PEG). The effects of various polymerization parameters on the size and morphology of droplets rich in PAM were systematically investigated. The droplet size and morphology was significantly influenced by the polymerization rate. The high polymerization rate caused the formation of stripe‐shaped droplets because of the aggregation of more droplets rapidly separated from the continuous phase. At the same time, the monomer partition behavior mainly relied on the temperature, and the PEG concentration also dramatically affected the droplet size and morphology. The increase in PEG concentration not only changed the monomer partition behavior and restrained droplet aggregation but also shortened the critical PAM radical chain length and accelerated the droplet formation. Furthermore, the stirring speed was also recognized as the correlative factor that affected the droplet stability and monomer diffusion rate from the continuous phase into the droplets. The addition of salt and alcohol altered the droplet stability and the final droplet size and morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

11.
A new aqueous two‐phase system (ATPS) based on a degradable polymer called poly(ethylene oxide sulfide) with a molecular weight of 33 000 g mol?1 (identified as PEOS‐12) and potassium phosphate was exploited for the potential recovery of proteins. An initial characterisation of the ATPS was achieved by the construction of a phase diagram for the PEOS‐12/phosphate system. The protein partitioning behaviour of lysozyme and bovine serum albumin (BSA), selected as single model proteins, and B‐phycoerythrin (BPE) produced by Porphyridium cruentum in the new ATPS under increasing tie line length (TLL) conditions at constant phase volume ratio (Vr) and system pH was investigated. Both single proteins partitioned in the new ATPS, initially exhibiting bottom phase preference; however, lysozyme changed phase preference when TLL was increased. Fractionation of a complex model (production of BPE by P. cruentum) using PEOS‐12/phosphate ATPS was performed to evaluate the potential protein recovery from fermentation broth or cell homogenate. The proposed new ATPS proved to be suitable for the potential recovery of BPE from crude extract of P. cruentum. In general, a system comprising Vr = 1.0, 18% (w/w) PEOS‐12, 8% (w/w) phosphate and 30% (w/w) TLL at pH 7.0 provided conditions to concentrate BPE into the bottom phase (i.e. partitioning behaviour of BPE; lnKBPE = ?1.8) with a protein recovery of 84%. The findings reported here demonstrate the potential application of the new ATPS for the recovery of proteins from complex biological suspensions. Copyright © 2006 Society of Chemical Industry  相似文献   

12.
The use of polymeric materials as the carrier in the controlled release of guest molecules has become an important research area in the polymeric materials science, because of their advantages of the safety, efficacy and patient convenience. One of them, star amphiphilic polymer can self‐assemble into supermolecular structure (polymer micelles) by the balance of hydrophilic and hydrophobic interaction. In this study, star amphiphilic copolymer consisting of hydrophobic and biodegradable poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene oxide) (PEO) blocks were synthesized by two‐step ring‐opening polymerization. The resultant polymer was characterizated by FTIR, 1H‐NMR, and DSC to determine its chemical structure. The morpholoy of the polymer micelles was analyzed by TEM. Using star‐PCL‐b‐PEO as carriers and congo red as model guest molecules, the encapsulation and release properties were investigated by UV–visable analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

13.
A series of thermosensitive copolymeric hydrogels were prepared from various molar ratios of N‐isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methylether acrylate (PEGMEAn), which was synthesized from acryloyl chloride and poly(ethylene glycol) mono methylether with three oxyethylene chain lengths. Investigation of the effect of the chain length of oxyethylene in PEGMEAn, and the amount of the PEGMEAn in the NIPAAm/PEGMEAn copolymeric gels, on swelling behavior in deionized water was the main purpose of this study. Results showed that the swelling ratio for the present copolymeric gels increased with increasing chain length of oxyethylene in PEGMEAn and also increased with increase in the amount of PEGMEAn in the copolymeric gels. However, the gel strength and effective crosslinking density of these gels decreased with increase in swelling ratio. Some kinetic parameters were also evaluated in this study. Finally, the drug release and drug delivery behavior for these gels were also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1683–1691, 2003  相似文献   

14.
A cationic poly(methyl iodide quaternized styrene–N,N‐dimethylaminopropylmaleamidic acid) copolymer was synthesized through amidoacidification reaction of styrene‐maleic anhydride copolymer with N,N‐dimethylaminopropylamine (ring‐opening reaction). Its properties in various aqueous salt solutions and pH solutions were studied by measurements of reduced viscosity and intrinsic viscosity. The results indicated that the reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the type and concentration of the added salts and the results also showed a contrary tendency in some salts with monovalent acid groups to polyelectrolyte. At the same time, some salt ions were observed to strongly attract the quaternary ammonium group of the cationic polymeric side chain and resulted in agglomeration of the polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1619–1626, 2001  相似文献   

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