Effect of Spacer and Mesogen in Side-Chain Liquid Crystal Elastomer Structure on Reversible Actuation Behavior

A liquid crystal elastomer (LCE) actuator is capable of displaying reversible shape change through order–disorder phase transition, and it is generally prepared by aligning the mesogens (often through mechanical stretching) and then cross-linking polymer chains. Herein, a series of four side-chain LCEs are synthesized by grafting side-group mesogens onto the middle block of the styrene–butadiene–styrene (SBS) triblock copolymer. These LCEs differ either in the length of the flexible spacer linking mesogen and chain backbone or in the mesogen used in their chemical structures. By means of polarized infrared spectroscopic and X-ray diffraction (XRD) measurements, the effects of spacer and mesogen on stretching-induced orientation of mesogens are investigated. The results show that varying the length of spacer or changing the mesogen has a profound effect on the orientation direction (parallel or perpendicular to the stretching direction), orientation degree (order parameter), and orientation stability to large strain. The characteristic orientation behaviors of the side-chain LCEs are retained in their respective actuators, i.e., stretched films subjected to photo-cross-linking and thermal equilibrium in the isotropic state, and determine their reversible actuation upon heating to the isotropic phase and cooling to the LC phase. In particular, the results confirm that in order for a side-chain LCE actuator to exhibit the unusual thermally induced auxetic-like shape change, i.e., its strip contracts in both length and width on heating and extends in both directions on cooling, the LCE must have a high and stable perpendicular orientation of mesogens that can compete with the conformational change of the main chain backbone aligned parallel to the stretching direction

Different Rotamer States of Cytosine Nucleobases in Heteronuclear PtPd-, PtPd₂, and Pt₂Pd₂Ag Complexes Derived from [Pt(2,2′-bpy)(1-MeC-<i>N3</i>)₂]²⁺ (1-MeC = 1-Methylcytosine): First Examples of Species with Head–Head Oriented 1-MeC^– Ligands

[Pt­(2,2′-bpy)­(1-MeC-<i>N3</i>)₂]­(NO₃)₂ (<b>1</b>) (2,2′-bpy = 2,2′-bipyridine; 1-MeC = 1-methylcytosine) exists in water in an equilibrium of head–tail and head–head rotamers, with the former exceeding the latter by a factor of ca. 20 at room temperature. Nevertheless, <b>1</b> reacts with (en)­Pd^II (en = ethylenediamine) to give preferentially the dinuclear complex [Pt­(2,2′-bpy)­(1-MeC^–-<i>N3,N4</i>)₂Pd­(en)]­(NO₃)₂·5H₂O (<b>2</b>) with head–head arranged 1-methylctosinato (1-MeC^–) ligands and Pd being coordinated to two exocyclic N4H^– positions. Addition of AgNO₃ to a solution of <b>2</b> leads to formation of a pentanuclear chain compound [{Pt­(2,2′-bpy)­(1-MeC^–)₂Pd­(en)}₂Ag]­(NO₃)₅·14H₂O (<b>5</b>) in which Ag⁺ cross-links two cations of <b>2</b> via the four available O2 sites of the 1-MeC^– ligands. <b>2</b> and <b>5</b> appear to be the first X-ray structurally characterized examples of di- and multinuclear complexes derived from a Pt^II species with two cis-positioned cytosinato ligands adopting a head–head arrangement. (tmeda)­Pd^II (tmeda = <i>N,N,N</i>′<i>,N</i>′-tetramethylethylenediamine) and (2,2′-bpy)­Pd^II behave differently toward <b>1</b> in that in their derivatives the head–tail orientation of the 1-MeC^– nucleobases is retained. In [Pt­(2,2′-bpy)­(1-MeC^–)₂{Pd­(2,2′-bpy)}₂]­(NO₃)₄·10H₂O (<b>4</b>), both (2,2′-bpy)­Pd^II entities are pairwise bonded to N4H^– and O2 sites of the two 1-MeC^– rings, whereas in [Pt­(2,2′-bpy)­(1-MeC^–)₂{Pd­(tmeda)}₂(NO₃)]­(NO₃)₃·5H₂O (<b>3</b>) only one of the two (tmeda)­Pd^II units is chelated to N4H^– and O2. The second (tmeda)­Pd^II is monofunctionally attached to a single N4H^– site. On the basis of these established binding patterns, ways to the formation of mixed Pt/Pd complexes and possible intermediates are proposed. The methylene protons of the en ligand in <b>2</b> are special in that they display two multiplets separated by 0.64 ppm in the ¹H NMR spectrum

Circularly Polarized Light with Sense and Wavelengths To Regulate Azobenzene Supramolecular Chirality in Optofluidic Medium

Circularly polarized light (CPL) as a massless physical force causes absolute asymmetric photosynthesis, photodestruction, and photoresolution. CPL handedness has long been believed to be the determining factor in the resulting product’s chirality. However, product chirality as a function of the CPL handedness, irradiation wavelength, and irradiation time has not yet been studied systematically. Herein, we investigate this topic using achiral polymethacrylate carrying achiral azobenzene as micrometer-size aggregates in an optofluidic medium with a tuned refractive index. Azobenzene chirality with a high degree of dissymmetry ratio (±1.3 × 10^–2 at 313 nm) was generated, inverted, and switched in multiple cycles by irradiation with monochromatic incoherent CPL (313, 365, 405, and 436 nm) for 20 s using a weak incoherent light source (≈ 30 μW·cm^–2). Moreover, the optical activity was retained for over 1 week in the dark. Photoinduced chirality was swapped by the irradiating wavelength, regardless of whether the CPL sense was the same. This scenario is similar to the so-called Cotton effect, which was first described in 1895. The tandem choice of both CPL sense and its wavelength was crucial for azobenzene chirality. Our experimental proof and theoretical simulation should provide new insight into the chirality of CPL-controlled molecules, supramolecules, and polymers

Comparison of healthy lifestyle behaviors among individuals with and without cardiovascular diseases from urban and rural areas in China: A cross-sectional study

<div><p>Introduction</p><p>The study aimed to explore the gap of prevalence of healthy lifestyle behaviors including smoking cessation, quitting drinking, physical activity and healthy eating between Chinese adults with and without cardiovascular diseases (CVDs).</p><p>Methods</p><p>This study is a cross-sectional component of Prospective Urban Rural Epidemiology (PURE)-China study, which recruited ~46,000 participants from 70 rural and 45 urban communities between 2005 and 2009. Participants were divided into disease (with CVDs) and control (without any diseases) groups. The adjusted rates were estimated for different strata by the generalized, linear mixed-effects model, including community as a random effect with additional adjustment for age, sex, education and income.</p><p>Results</p><p>Among 40,490 participants, <10% had all four healthy lifestyle behaviors (disease group versus control group: urban areas: 7.8% versus 8.1%; rural areas: 3.4% versus 3.2%). The rates of smoking cessation and quitting drinking were significantly higher in disease group for both urban and rural residents (P<0.001). In urban areas, higher rates were observed in all other three healthy lifestyle behaviors except physical activity in low-income regions (P<0.05). Similarly, the higher trends were observed for stopping smoking and drinking while opposite trends for healthy eating among rural residents from low-income regions (P<0.05).</p><p>Conclusions</p><p>Our study showed that the prevalence of adopting all four behaviors was low among Chinese adults. Individuals with CVDs were more likely to follow healthy lifestyle behaviors, but it still indicated a large gap between the actual and ideal adoption of healthy lifestyle behaviors, which called for the promotion of population-wide strategies to modify lifestyle behaviors in addition to individual health-care intervention strategies.</p></div

Adjusted prevalence of adoption of 2 or more healthy lifestyle behaviors by number of diseases.

<p>Adjusted prevalence of adoption of 2 or more healthy lifestyle behaviors by number of diseases.</p

Baseline characteristics of participants with and without cardiovascular diseases.

<p>Baseline characteristics of participants with and without cardiovascular diseases.</p

Copper-Catalyzed Direct Oxidative C–H Functionalization of Unactivated Cycloalkanes into Cycloalkyl Benzo[<i>b</i>]phosphole Oxides

The first simple and efficient Cu-catalyzed radical addition/cyclization of various unactivated cycloalkanes with diaryl­(arylethynyl)-phosphine oxides has been developed, providing a general, one-step approach to construct a new class of important benzo­[<i>b</i>]­phosphole oxides via sequential C–H functionalization along with two new C–C bond formations

Participant enrollment and study population identification.

<p>Participant enrollment and study population identification.</p

Adjusted prevalence^a of smoking cessation, quitting drinking, high level of physical activity and healthy eating.

<p>Adjusted prevalence<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181981#t002fn001" target="_blank">^a</a> of smoking cessation, quitting drinking, high level of physical activity and healthy eating.</p

The rates of ever use and current use of E-Cigarettes and Snus.

<p>The rates of ever use and current use of E-Cigarettes and Snus.</p