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
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 CO 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
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
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
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
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
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
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
<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