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Kwon, Hyuck Joon; Osada, Yoshihito; Gong, Jian Ping
doi: 10.1295/polymj.PJ2006125pmid: N/A
Polyelectrolyte gels are charged polymer networks with macro-ions fixed on polymer chains. This present paper introduces fundamental aspects, properties and application of negatively charged polyelectrolyte gels, focusing on the electrical properties of polyelectrolyte gels, diffusion of proteins in polyelectrolyte gels, interactions between polyelectrolyte gels and oppositely charged molecules, and mechanical strength of polyelectrolyte based gels. These characteristic properties of polyelectrolyte gels have considerable potential for applications, such as soft and wet scaffolds of cells, soft actuators and replacement of biological tissues.
doi: 10.1295/polymj.PJ2006061pmid: N/A
The preceding theory of gelation is extended to the multilink system of the R–A g +R–B f−g model, where the branching process proceeds forming junction points each comprising of J/2 A FU’s and J/2 B FU’s. We show that there exists a neat solution of the ring concentration for this generalized system; the mathematics is identical with the previous finding, but the expression is greatly simplified. Making use of this result together with the random distribution assumption of cyclic bonds, we derive the closed expression of the gel point for this new gelling system which is expected to have wider application.
Yanagimoto, Yasushi; Takaguchi, Yutaka; Tuboi, Sadao
doi: 10.1295/polymj.PJ2006082pmid: N/A
Novel surface-block dendrimer was synthesized via a divergent/convergent approach using [4+4] photocycloaddition of two different anthracenes bearing a newly designed dendritic substituent, of which terminal groups are long alkyl chains for one hemisphere and oligo(ethylene oxide) chains for the other hemisphere. A solution of the two different anthryl dendrons was irradiated with a high-pressure mercury lamp to afford a hetero-dimer, which consists of the two different dendrons. The surface-block dendrimer was isolated by the use of size exclusion chromatography (SEC) and well characterized by NMR spectrum, SEC, and MALDI-TOF-Mass spectrum. Furthermore, this paper describes a ratio of the photoproducts (the hetero-dimer and two homo-dimers) that were obtained from the photocycloaddition reactions carried out in neat and an emulsion condition, along with the solution.
Okamura, Haruyuki; Shin, Kazuo; Shirai, Masamitsu
doi: 10.1295/polymj.PJ2006007pmid: N/A
Multifunctional crosslinkers having two, three, four and six functionalities were synthesized using a convergent method and were applied to a photocrosslinking system having thermally degradable properties. The multifunctional crosslinkers contained epoxy units and tertiary ester linkages. When the blended films of epoxides/poly(p-vinylphenol) with a photoacid generator were irradiated and followed by baking at relatively lower temperatures (<100 °C), the films became insoluble in solvents. Heating conditions strongly affected the insoluble fraction of the blends. Insoluble fraction of the blended films increased with the number of the epoxy unit of a molecule. The crosslinked films became soluble after prolonged bake at relatively higher treatments (>120 °C). The reaction pathway of the blended system was studied by in situ FT-IR measurements.
Li, Qiuying; Wu, Guozhang; Zhang, Xiliang; Wu, Chifei
doi: 10.1295/polymj.PJ2006053pmid: N/A
The encapsulation of poly (n-butyl acrylates) (PBA) onto carbon black (CB) surface via ultrasonic irradiation initiating emulsion polymerization was investigated. The results showed that the route performed at ambient temperature can efficiently prepare PBA encapsulated CB as proved by the aggregation of PBA encapsulated CB in the precipitator of PBA. The surface properties of CB coated with PBA were analyzed by FT-IR and XPS. The content of PBA encapsulated on the CB surface reaches 11.87% determined by TGA. Compared with the conventional chemical modification of CB, it was found that the particle size of CB obtained by the present approach can be controlled, and dynamic light scattering results quantified that CB particles with narrower size distribution and smaller size were obtained. The PBA encapsulated CB can be dispersed uniformly in the polymer matrix.
Yang, Junliang; Zhao, Ting; Liu, Leijing; Zhou, Yunchun; Li, Gao; Zhou, Enle; Chen, Xuesi
doi: 10.1295/polymj.PJ2006094pmid: N/A
Isothermal crystallization kinetics and morphology of the poly(L-lactide) block in poly(L-lactide)-poly(ethylene glycol) diblock copolymers were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), respectively. The results were compared with that of the PLLA homopolymer. The introduction of the PEG block accelerated the crystallization rate of the PLLA block and promoted to form ring-banded spherulites. The analysis of isothermal crystallization kinetics has shown that the PLLA homopolymer accorded with the Avrami equation. But the PLLA block of the diblock copolymers deviated from the Avrami equation, which resulted from increasing of the crystallization rate and occurring of the second crystallization process. The equilibrium melting temperature (T m o ) of the PLLA block fell with its molecular weight decreasing. The conditions to obtain more regular ring-banded spherulites were below: the sample was the PLLA block of LA5EG5; the crystallization temperature was about from 95 °C to 100 °C, which almost corresponded to regime II.
Hoshikawa, Naohiro; Yamamoto, Chiyo; Hotta, Yuji; Okamoto, Yoshio
doi: 10.1295/polymj.PJ2006087pmid: N/A
N-(Triphenylmethyl)methacrylamide (TrMAM) and N-[di(4-butylphenyl)-phenylmethyl]methacrylamide (DBuTrMAM) were polymerized using a radical initiator. The obtained poly(TrMAM) was insoluble in common organic solvents, but poly(DBuTrMAM) was soluble in chloroform and THF. Both polymers were dissolved in conc. H2SO4 accompanied by cleavage of the side groups to give poly(methacrylamide) (poly(MAM)). The 1H NMR of the polymers in D2SO4 indicated that the polymers obtained at low temperature were nearly 100% isotactic. The poly(MAM) with almost 100% isotacticity showed a crystallinity. The poly(DBuTrMAM) formed a lyotropic crystalline phase in chloroform. The radical polymerization of the monomers in the presence of various chiral additives produced optically active polymers having a prevailing helicity. The optically active poly(TrMAM) exhibited a low chiral recognition.
Einaga, Yoshiyuki; Kito, Yumi; Watanabe, Mikiko
doi: 10.1295/polymj.PJ2006100pmid: N/A
The wormlike micelles formed with the binary mixtures of surfactant polyoxyethylene alkyl ethers (C i E j ), C10E6 + C14E6 and C14E8 + C14E6, were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The observed Kc/ΔR 0 as a function of the surfactant concentration c have been successfully analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass M w(c) of the micelle as a function of c along with the cross-sectional diameter d of the micelle. The mean-square radius of gyration <S 2> and the hydrodynamic radius R H as functions of M w have been well described by the theories for the wormlike spherocylinder model. The length of the micelles at fixed c and temperature T steeply increases with increasing weight fraction w t of C14E6 in both of the surfactant mixtures, implying that the micelles greatly grow in length when the surfactant component with longer alkyl group or with shorter oxyethylene group increases in the mixture. The results are in line with the findings for the micelles of the single surfactant systems where the C i E j micelles grow in length to a greater extent for larger i and smaller j. Although the values of d do not significantly vary with composition of the surfactant mixture, the stiffness parameter λ−1 remarkably decreases with w t in both of the mixtures, indicating that the stiffness of the micelle is controlled by the relative strength of the repulsive force due to the hydrophilic interactions between oxyethylen groups to the attractive one due to the hydrophobic interactions between alkyl groups among the surfactant molecules.
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