37 research outputs found

    Design of Polyurethane Composed of Only Hard Main Chain with Oligo(ethylene glycol) Units as Side Chain Simultaneously Achieved High Biocompatible and Mechanical Properties

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    In order to create a novel rigid polymer material for biomedical application, we designed the polymer structure of polyurethane, bearing oligo­(ethylene glycol) (OEG) as the side chain, which was synthesized by only hard main chain using diisocyanate and short diol monomers. We investigated the effect of the graft structure of OEG units on polymer properties using pentaethylene glycol (OEG<sub>5</sub>) or propanediol (PDO) in the main chain as the other diol monomers. Furthermore, the rigid 4,4′-methylene­bis­(cyclohexyl isocyanate) (HMDI) and symmetric hexamethylene diisocyanate (HDI) were selected for the isocyanate monomers. As a result, there is a significant difference in various properties, depending on both the existence and the position of OEG units in the polymer structure. For example, differential scanning calorimetry (DSC) showed that the graft structure of OEG caused a decrease in the glass transition temperature from 73 to 35 °C in the case of using HMDI as well as a disappearance of the melting point in the case of using HDI. The Fourier transform infrared (FT-IR) spectra showed that the ordered hydrogen bonding of CO stretching vibration at 1682 cm<sup>–1</sup> was not observed in the polyurethane grafted with OEG. In the mechanical test of polyurethane composed of HMDI, the sample grafted with OEG exhibited excellent values of elastic modulus of 1.7 GPa and elongation at break of 184%, while that with OEG<sub>5</sub> and PDO in the main chain showed 115 MPa with 370% and 739 MPa with 19%, respectively. The polyurethane grafted with OEG showed around 0.6 μg/cm<sup>2</sup> of protein adsorption, almost the same as that with OEG<sub>5</sub> in the main chain, while that using PDO in the main chain showed more than 3.0 μg/cm<sup>2</sup>. Therefore, the polyurethane design bearing OEG as the side chain provides excellent rigidity, toughness, and biocompatibility simultaneously

    Synthesis and Star/Linear Topology Transformation of a Mechanically Linked ABC Terpolymer

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    The synthesis of an ABC star terpolymer containing one polymer chain connected mechanically through a rotaxane linkage and its topology transformation to a linear structure are reported. Pseudo[2]­rotaxane, which was designed as the key trifunctional species for the star polymer synthesis, comprised a <i>sec</i>-ammonium axle with ethynyl and hydroxy groups and a crown ether wheel with a trithiocarbonate group. Stepwise polymer connections to the pseudo[2]­rotaxane using the three groups afforded a rotaxane-linked ABC star terpolymer. The topology transformation from star to linear by the removal of the attractive interaction between the axle and wheel components yielded a linear ABC terpolymer via the wheel shifting to the axle end. The spectroscopic and solution property changes clearly indicated the occurrence of the polymer topology change

    Mechanically Linked Block/Graft Copolymers: Effective Synthesis via Functional Macromolecular [2]Rotaxanes

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    An effective method to synthesize mechanically linked transformable block polymer was developed utilizing functional macromolecular [2]­rotaxane with a “fixed” or “movable” wheel. The interaction between a <i>sec</i>-ammonium and a dibenzo-24-crown-8-ether was the key to control the mobility of the wheel component, indicating the capability of the transformation from linear block copolymer to block/graft copolymer in which the grafting polymer chain is movable along the axle polymer chain

    Multicolor Mechanochromic Polymer Blends That Can Discriminate between Stretching and Grinding

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    Mechanochromic polymers, which react to mechanical force by changing color, are expected to find applications in smart materials such as damage sensors. Although numerous types of mechanochromic polymers have been reported so far, developing mechanochromic polymers that can recognize different mechanical stimuli remains a formidable challenge. Materials that not only change their color in response to a mechanical stimulus but also detect its nature should be of great importance for practical applications. In this paper, we report our preliminary findings on multicolor mechanochromic polymer blends that can discriminate between two different mechanical stimuli, i.e., stretching and grinding, by simply blending two mechanochromic polymers with different architectures. The rational design and blending of two mechanochromic polymers with radical-type mechanochromophores embedded separately in positions adjacent to soft or hard domains made it possible to achieve multicolor mechanochromism in response to different stimuli. Electron paramagnetic resonance and solid-state UV–vis measurements supported the mechanism proposed for this discrimination

    Effective Approach to Cyclic Polymer from Linear Polymer: Synthesis and Transformation of Macromolecular [1]Rotaxane

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    We report a convenient and scalable synthesis of cyclic poly­(ε-caprolactone) (PCL) from its linear counterpart based on the rotaxane protocol. Cyclic PCL was prepared by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by a pseudo[2]­rotaxane initiator in the presence of diphenylphosphate (DPP) as a catalyst, followed by capping of the propagation end by using a bulky isocyanate to afford macromolecular [2]­rotaxane. The successive intramolecular cyclization to macromolecular [1]­rotaxane at the polymer terminus proceeded with good yield. The attractive interaction of the terminal ammonium/crown ether moiety was removed via N-acetylation. This enabled movement of the crown ether wheel along the axle PCL chain to the urethane region of the other terminus in solution state. Size-exclusion chromatography and 2D diffusion-ordered spectroscopy (DOSY) results demonstrated the formation of cyclic PCL from linear PCL, which is further supported by thermal property or crystallinity change before and after transformation

    Macromolecular [2]Rotaxanes: Effective Synthesis and Characterization

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    Macromolecular [2]­rotaxanes, which consist of a polymer chain threading into a wheel component, were synthesized in high yield and with high purity. The synthesis was achieved by the ring-opening polymerization (ROP) of δ-valerolactone (VL) using a hydroxyl-terminated pseudorotaxane as an initiator with diphenyl phosphate as a catalyst in dichloromethane at room temperature. The <sup>1</sup>H NMR, gel permeation chromatography (GPC), and MALDI-TOF-MS measurements of the resulting poly­(δ-valerolactone)­s clearly indicate the presence of the rotaxane structure with the polymer chain, confirming that the diphenyl phosphate-catalyzed ROP of VL proceeds without deslippage of the wheel component. The obtained macromolecular [2]­rotaxane was acetylated to afford a nonionic macromolecular [2]­rotaxane, in which only one wheel component is movable from one end to another along the polymer chain

    Synthesis of Vinylic Macromolecular Rotaxane Cross-Linkers Endowing Network Polymers with Toughness

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    Macromolecular rotaxane cross-linkers having two radically polymerizable vinyl groups (RCs) were first synthesized and used to prepare network polymers. A crown ether/<i>sec-</i>ammonium-type pseudorotaxane initiator having an OH terminal-containing axle and a crown ether wheel with a vinyl group was subjected to the living ring-opening polymerization of δ-valerolactone followed by end-capping with a bulky isocyanate to yield a polyester axle-tethering macromolecular [2]­rotaxane cross-linker (RC). Rotaxane cross-linked polymers (RCPs) were prepared by the radical polymerization of <i>n</i>-butyl acrylate in the presence of RCs (0.25, 0.50 mol %). The properties of the RCPs and covalently cross-linked polymers (CCPs) were characterized mainly by mechanical properties. Both fracture stress and strain values of RCPs were much higher than those of CCPs, probably owing to the increased network homogeneity by the rotaxane cross-link. The hybrid-type RCPs obtained from a mixture of RC and covalently connected cross-linker (CC) showed poorer mechanical properties similar to that of CCPs, indicating the importance of RCs in increasing the toughness of the network polymers

    Survey of Attitudes toward Uterus Transplantation among Japanese Women of Reproductive Age: A Cross-Sectional Study

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    <div><p>Objective</p><p>Uterus transplantation (UTx) is a potential option for women with uterine factor infertility to have a child, but there has been no large-scale survey of the views on UTx in women of reproductive age in Japan. The present study was aimed to clarify the views of Japanese women of reproductive age on UTx for uterine factor infertility.</p><p>Methods</p><p>A questionnaire on UTx was conducted by an Internet research company in December 2014 as a cross-sectional study in 3,892 randomly chosen women aged 25 to 39 years old. Responses were analyzed from 3,098 subjects (mean age 32.1±4.2 years old), after exclusion of inappropriate respondents in screening.</p><p>Results</p><p>Of the respondents, 62.1%, 34.7% and 18.1% favored adoption, UTx and gestational surrogacy, respectively. In contrast, 7.0%, 21.9% and 63.3% opposed adoption, UTx and gestational surrogacy, respectively. In choices of candidates for UTx based on highest priority, deceased persons (33.8%) and mothers (19.0%) were favored as donors, and women with congenital absence of the uterus (54.4%) and hysterectomy due to a malignant uterine tumor (20.0%) as recipients. Regarding societal acceptance of UTx, the answer rates were 15.7% for "UTx should be permitted", 77.6% for "UTx should be permitted with discussion", and 6.7% for "UTx should not be permitted, even with discussion". Regarding personal opinions on UTx, 44.2% were in favor, 47.5% had no opinion, and 8.3% were against.</p><p>Conclusion</p><p>Our results suggest that many Japanese women of reproductive age feel that UTx is socially and individually acceptable, but that concerns requiring further discussion remain among these women. There was also a tendency for UTx to be viewed more favorably than gestational surrogacy.</p></div
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