Polymer Journal

Li, Junfang; Ngai, To; Wu, Chi

doi: 10.1038/pj.2010.59pmid: N/A

In the past, many laser light-scattering experimental results revealed that besides the fast relaxation mode, there existed an additional slow mode in semidilute solutions. This slow mode has been assigned to a variety of origins, but there has been no clear and well-accepted explanation. As the polymer concentration increases, the slow relaxation mode persists in the concentrated region, in melts and in gels in which polymer chains are crosslinked instead of entangled. The slow relaxation mode has also been reported for charged macromolecules in aqueous and nonaqueous solutions. However, it is generally thought to be different in nature from that observed in semidilute neutral polymer solution. In recent years, armed with novel solution preparation methods and some specially designed polymers, we have reexamined the dynamics of polymer chains, especially the slow mode, in semidilute neutral polymer solutions, dilute polyelectrolyte solutions and gels, which are reviewed here. Our results suggest that the slow mode can be qualitatively considered as hindered motions of interacting chains even though the nature of interaction can be very different; namely, from the weak segment–segment interaction in a less good solvent to strong electrostatic interaction among polyelectrolyte chains, and even to chemical crosslinking inside gel networks.

Fuchise, Keita; Sone, Masako; Miura, Yutaka; Sakai, Ryosuke; Narumi, Atsushi; Sato, Shin-Ichiro; Satoh, Toshifumi; Kakuchi, Toyoji

doi: 10.1038/pj.2010.55pmid: N/A

1-Adamantyl methacrylate (AdMA) was polymerized using the atom transfer radical polymerization (ATRP) method with methyl α-bromoisobutyrate (MBiB), copper(I) bromide (CuBr), copper(II) bromide (CuBr2) and 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) in toluene at 60 °C, producing well-defined poly(1-adamantyl methacrylate) (PAdMA). Simultaneous control of the molecular weight and tacticity of PAdMA was successfully achieved by the ATRP method using the MBiB/CuBr/CuBr2/tris[2-(dimethylamino)ethyl]amine-initiating system in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) at −20 °C. Block copolymerization of AdMA and methyl methacrylate (MMA) was successfully achieved by the poly(methyl methacrylate) macroinitiator/CuBr2/HMTETA/tin(II) 2-ethylhexanoate-initiating system based on activators generated by electron transfer (AGET) ATRP method. Differential scanning calorimetry revealed the relationship between the glass transition temperature, molecular weight and tacticity of the obtained PAdMA.

Azechi, Motohisa; Yamabuki, Kazuhiro; Onimura, Kenjiro; Oishi, Tsutomu

doi: 10.1038/pj.2010.54pmid: N/A

Asymmetric anionic homopolymerization of N-4′-benzo 15-crown-5 maleimide (B15C5MI) was carried out with a chiral anionic initiator consisting of organometal (n-butyllithium, diethylzinc (Et2Zn)) and chiral ligand ((–)-sparteine ((–)-Sp), (S, S)-(1-ethylpropylidene)-bis(4-benzyl-2-oxazoline) ((S, S)-Bnbox)) to obtain optically active polymers. The polymer obtained with the chiral ligand had an optical rotation, suggesting that asymmetric induction occurred on the main chain of the polymer. Poly(B15C5MI) obtained with Et2Zn/(S, S)-Bnbox in tetrahydrofuran showed the highest specific rotation of −64.1°. The chiroptical properties and structures of the polymers obtained were analyzed by circular dichroism, ultraviolet, nuclear magnetic resonance and gel permeation chromatography measurements. The effects of adding (R)-cyclohexylethylamine to the obtained poly(B15C5MI) were investigated.

Hosseini, Seyed Hossein; Malekdar, Maryam; Naghdi, Shaghayegh

doi: 10.1038/pj.2010.56pmid: N/A

A strategy was used to control the crosslinking of polyaniline (PANi) to allow the synthesis of high-molecular-weight, conductive copolymers. Aniline sulfide resin (ASR) was synthesized by the reaction of aniline and sulfide dichloride. Crosslinked ASR (ASC) was prepared in the presence of ammonium peroxydisulfate and aniline in an aqueous solution as the oxidant and monomer, respectively. The graft copolymer was obtained by oxidizing aniline on ASR in the presence of an initiator and an excess amount of aniline, in which the aniline was oxidized to form PANi through a radical cation mechanism. By changing the ratio of ASR to aniline during the polymerization reaction, it was possible to control the number of crosslinked sites, the electrical conductivity, the molecular weight and the solubility. The structure was characterized by spectroscopic data. The method introduced here describes a strategy for controlling the molecular weight of PANi and in turn its physical properties. This approach may be extended to the synthesis and modification of other polymers. Electropolymerization was carried out by coating ASR on the surface of a glassy carbon disk electrode and then growing this on graft copolymer ASC in the presence of fresh aniline and an acidic solution. The electrical conductivity of ASC was studied by a four-point probe method and produced a conductivity of 8.5 × 10−3 S cm–1.

Ghaemy, Mousa; Amini Nasab, Seyed Mojtaba

doi: 10.1038/pj.2010.57pmid: N/A

Novel fluorescent polyimides (PIs) were prepared from a new diamine, 4-(4-(4-amino-2-(4,5-diphenyl-1H-imidazol-2-yl)phenoxy)phenoxy)-3-(4,5-diphenyl-1H-imidazol-2-yl)benzenamine, and three tetracarboxylic dianhydrides. The new symmetrical diamine was successfully synthesized by the nucleophilic substitution reaction of hydroquinone with 2-(2-chloro- 5-nitrophenyl)-4, 5-diphenyl-1H-imidazole (I). The PIs synthesized here are amorphous and soluble in polar aprotic solvents and demonstrate the ability to form films; their inherent viscosities ranged from 43 to 82 ml g−1. The PIs had suitable thermal stability and relatively high T g values (245–274 °C), 10% weight loss temperatures in excess of 500 °C and char yields at 600 °C in air up to 62%. The PIs show emission in the solid state and in dilute (0.20 g per 100 ml) N,N-dimethyl acetamide solution at 431–464 nm with photoluminescence (PL) quantum yields in the range of 11–25%. The chemiluminescence activity of PIs in the presence of peroxyoxalate was also investigated.

Kang, Young Ah; Kim, Kyoung Hou; Ikehata, Soichiro; Ohkoshi, Yutaka; Gotoh, Yasuo; Nagura, Masanobu; Koide, Mitsuharu; Urakawa, Hiroshi

doi: 10.1038/pj.2010.53pmid: N/A

Rapid and uniform heating by CO2 laser radiation can fix the position where necking occurs. Therefore, this study investigated the development of a fiber structure in poly(vinylidene fluoride) in continuous drawing by in situ measurement using synchrotron X-ray radiation with a time resolution of several hundred microseconds. Two neck-deformation behaviors were observed in the laser drawing: a moderate neck deformation under low drawing stress and a steep neck deformation under high drawing stress. The low drawing stress resulted in a mixture of α- and β-crystals in which the β-crystal was formed within 1 ms after the necking, earlier than the α-crystal. The development of the fiber structure under high drawing stress was almost complete in less than 1 ms, and the developed structure contained only β-crystals. Small-angle X-ray scattering images showed meridional streaks at low drawing stress, whereas a four-pointed pattern occurred under high drawing stress. Low drawing stress generated a long periodic structure that was defective in the periodic regularity of crystalline and amorphous regions, although the molecular chains were nearly oriented along the fiber axis. The high drawing stress resulted in a well-packed structure of adjacent fibrils with alternating amorphous and crystalline regions.

Damaceanu, Mariana-Dana; Rusu, Radu-Dan; Bruma, Maria; Jarzabek, Bozena

doi: 10.1038/pj.2010.49pmid: N/A

Two series of poly(oxadiazole-imide)s based on naphthalene-containing anhydrides and aromatic diamines containing preformed oxadiazole rings have been synthesized and their properties studied and compared. One series contains four polymers: two of them are based on naphthalene-1,4,5,8-tetracarboxylic dianhydride and the other two are based on bis(ketonaphthalic-anhydride). The other series contains four copolymers based on mixtures of these dianhydrides with hexafluoroisopropylidene-diphthalic anhydride. The thermal stability of these polymers and copolymers and their photo-optical properties in solution and solid state have been investigated.

Nakajima, Haruki; Komatsu, Hiroshi; Iikura, Hitoe; Igarashi, Tetsutaro; Sakurai, Tadamitsu

doi: 10.1038/pj.2010.51pmid: N/A

Aryl substituent effects on photoinduced refractive index changes were investigated with the use of poly(methyl methacrylate) (PMMA) films doped with (Z)-N-acetyl-α-dehydroarylalanine naphthyl esters ((Z)-1). Upon irradiation with Pyrex-filtered or unfiltered light from a high-pressure mercury lamp, (Z)-1 underwent heterolytic cleavage of the ester C(=O)–O bond preferentially in both solution and PMMA film to afford arylmethylene-substituted (Z) oxazolone and naphthol derivatives as major products, irrespective of the aryl substituents introduced. Irradiation of (Z)-1 in the film with the unfiltered light enabled much more rapid photochemical transformation into the oxazolones and the intense ultraviolet absorption shifted to longer wavelength relative to that of the starting naphthyl esters. Analysis of the aryl substituent effects confirmed that the PMMA/(Z)-1 system, in which 1-naphthylmethylene-substituted oxazolone was formed along with 1-naphthol, enhanced the refractive index of this polymer film by as much as 0.020.

Tanaka, Yuka; Naka, Kensuke

doi: 10.1038/pj.2010.50pmid: N/A

Size-controlled calcium carbonate particles were obtained using a ‘carbonate controlled-addition method’ with G0.5 poly(amidoamine) (PAMAM) dendrimer with carboxylate groups at the external surface. An aqueous ammonium carbonate solution was added to an aqueous solution of the dendrimer and CaCl2 at different time periods (3 min, 1 h or 24 h) and was stirred for 1 day. Both crystal phases obtained at incubation times of 1 and 24 h were vaterite. The dendrimer–CaCl2 solution incubated for 3 min produced vaterite particles that coexisted with calcite. The average particle size of the spheres decreased from 2.2±0.2 to 0.61±0.24 μm with an increase in the incubation time of the dendrimer–CaCl2 solution. When the products were kept in the reaction mixtures for 3 days, the CaCO3 phase of the precipitates obtained after incubating the dendrimer–CaCl2 solution for 3 min and 1 h was calcite. However, the product obtained after incubating for 24 h was vaterite. The present results demonstrate that the interaction and the reaction kinetics of the dendrimer–Ca2+ complex have an important role in the mineralization and stabilization of CaCO3 particles.

Gunji, Takahiro; Shigematsu, Yasunobu; Kajiwara, Takashi; Abe, Yoshimoto

doi: 10.1038/pj.2010.52pmid: N/A

3-Mercaptopropyl(trimethoxy)silane (MTMS)/1,2-bis(triethoxysilyl)ethane copolymer was synthesized by the hydrolytic polycondensation of the two alkoxysilanes in the presence of hydrochloric acid as a catalyst under nitrogen flow. Free-standing films were prepared by heating the copolymer at 80 °C for 4 days. The films were dipped in a 30% hydrogen peroxide solution at room temperature for 4 days. The sulfonated films were stable against hydrolysis and maintained their form at 150 °C. The sulfonyl group content of the film at 150 °C was 1.20 mmol g−1 when the composition of MTMS/1,2-bis(trimethoxysilyl)ethane was 1:2.