Dual Cross-linked Vinyl Vitrimer with Efficient Self-Catalysis Achieving Triple-Shape-Memory Properties.

As an emerging class of dynamic cross-linked network, vitrimers have attracted much attention due to the combination of mechanical advantages of thermosets and recyclability of thermoplastics at an elevated temperature. In particular, most vitrimers with multi-shape memory properties usually involve more than one thermal transition or molecular switch, which might pose a challenge for facile sample fabrication and potentially limits their applications. In pursuit of a more universal and simple route, utilizing commercially available and inexpensive reagents to prepare shape-memory vitrimers with dual cross-linked network from vinyl monomer-derived prepolymers is reported here. Copolymerization of desired vinyl monomers gives prepolymers containing carboxyl and zinc carboxylate groups, which are later converted into vitrimers in a single step by post-curing with diglycidylether of bisphenol A. The Zn2+ ions can not only act as physical crosslinking points through ionic coordination interactions, thus providing the triple-shape-memory properties, but also play the role of catalyst to activate transesterification in the dynamic covalent network. This new self-catalyzed vitrimer has excellent transesterification efficiency, triple-shape-memory properties, and can be sufficiently healed and reprocessed at an elevated temperature. The proposed molecular design of self-catalyzed materials opens a new avenue toward commercially relevant fabrication of high-performance vitrimers with multiple shape-memory properties.

A Single Molecular Diels-Alder Crosslinker for Achieving Recyclable Cross-Linked Polymers.

A triol-functional crosslinker combining the thermoreversible properties of Diels-Alder (DA) adducts in one molecule is designed, synthesized, and used as an ideal substitute of a traditional crosslinker to prepare thermal recyclable cross-linked polyurethanes with excellent mechanical properties and recyclability in a very simple and efficient way. The recycle property of these materials achieved by the DA/retro-DA reaction at a suitable temperature is verified by differential scanning calorimetry and in situ variable temperature solid-state NMR experiments during the cyclic heating and cooling processes. The thermal recyclability and remending ability of the bulk polyurethanes is demonstrated by three polymer processing methods, including hot-press molding, injection molding, and solution casting. It is notable that all the recycled cross-linked polymers display nearly invariable elongation/stress at break compared to the as-synthesized samples. Further end-group functionalization of this single molecular DA crosslinker provides the potential in preparing a wide range of recyclable cross-linked polymers.

Relationship between the position of the mental foramen and the anterior loop of the inferior alveolar nerve as determined by cone beam computed tomography combined with mimics.

OBJECTIVE: The position of the mental foramen and the anterior loop length of the inferior alveolar nerve serve as important anatomical landmarks for surgical procedures in the anterior mandibular region. The purpose of this study was to determine the relationship between the anterior loop of the inferior alveolar nerve and the mental foramen by combining cone beam computed tomography and Mimics, a software used to construct 3-dimensional (3D) interactive models of anatomical structures. METHODS: Cone beam computed tomography images from a total of 60 patients were obtained and studied using GALAXY viewer or were imported into Mimics. The anterior loop of the inferior alveolar nerve was reconstructed 3-dimensionally, and then relevant parameters were measured. RESULTS: The parameters were measured, and their values include mean (SD) anterior loop length, 1.16 (1.78) mm; anterior loop angle, 19.13 (26.89) degrees; inferior alveolar canal diameter, 3.01 (0.67) mm; height of the inferior alveolar canal, 10.32 (1.56) mm; 2-dimensional mental foramen diameter, 2.97 (0.61) mm; 3D mental foramen diameter, 2.95 (0.59) mm; 2-dimensional vertical height of the mental foramen, 14.67 (1.67) mm; and 3D vertical height of the mental foramen, 14.61 (1.69) mm. The mental foramen was located apically between the first and second premolars in 51.67% and below the second premolar in 40.83% of the cases. CONCLUSIONS: A relationship was observed between the location of the mental foramen and the presence of the anterior loop of the inferior alveolar nerve. We highlight the effectiveness of cone beam computed tomography and 3D reconstruction in the identification of important anatomical structures relevant for preoperative assessment for surgical procedures in the anterior region of the mandible.

Bismuth-Decorated Beta Zeolites Catalysts for Highly Selective Catalytic Oxidation of Cellulose to Biomass-Derived Glycolic Acid.

Catalytic conversion of cellulose to liquid fuel and highly valuable platform chemicals remains a critical and challenging process. Here, bismuth-decorated ß zeolite catalysts (Bi/ß) were exploited for highly efficient hydrolysis and selective oxidation of cellulose to biomass-derived glycolic acid in an O2 atmosphere, which exhibited an exceptionally catalytic activity and high selectivity as well as excellent reusability. It was interestingly found that as high as 75.6% yield of glycolic acid over 2.3 wt% Bi/ß was achieved from cellulose at 180 °C for 16 h, which was superior to previously reported catalysts. Experimental results combined with characterization revealed that the synergetic effect between oxidation active sites from Bi species and surface acidity on H-ß together with appropriate total surface acidity significantly facilitated the chemoselectivity towards the production of glycolic acid in the direct, one-pot conversion of cellulose. This study will shed light on rationally designing Bi-based heterogeneous catalysts for sustainably generating glycolic acid from renewable biomass resources in the future.

Bioinspired Polyurethane Using Multifunctional Block Modules with Synergistic Dynamic Bonds.

Nature embraces an intriguing strategy to create high-performance biomaterials, such as spider silk which presents an unparalleled combination of stiffness, tensile strength, and toughness via hierarchical structures. However, to fabricate synthetic polymers with such excellent properties remains a challenging task. Inspired by the integration of multiblock backbone and densely H-bonding assemblies in spider silk as well as the delicate iron-catecholate complexes in mussel byssus, we proposed a novel molecular design with multifunctional block modules to obtain polymer materials that exhibit excellent mechanical property, self-healing ability, and reprocessability. It was achieved by introducing reversible iron-catechol (DOPA-Fe3+) cross-links and quadruple H-bonds bearing 2-ureido-4-[1H]-pyrimidinone (UPy) dimers as multifunctional blocks into a segmented polyurethane backbone with urethane blocks and semicrystalline polycaprolactone (PCL) blocks. These two types of dynamic cross-linking knots served as the sacrificial bonds to dissipate energy efficiently under external stress burden, endowing the dual physical cross-linked networks with increased toughness and breaking elongation. Moreover, the DOPA-Fe3+ complexes could increase the crystallization of PCL, leading to remarkably enhanced Young's modulus and tensile strength. Solid-state NMR revealed the formation of quadruple H-bonds in UPy dimers and the presence of DOPA-Fe3+ complexes, which restricted the mobility of the mobile phase and enhanced the crystallinity of the PCL domain. This work provides a feasible way to develop bioinspired materials with self-healable and reprocessable features, in addition to balanced enhancement of both stiffness and toughness.

A Chromosome-Scale Genome Assembly of Paper Mulberry (Broussonetia papyrifera) Provides New Insights into Its Forage and Papermaking Usage.

Paper mulberry (Broussonetia papyrifera) is a well-known woody tree historically used for Cai Lun papermaking, one of the four great inventions of ancient China. More recently, Paper mulberry has also been used as forage to address the shortage of feedstuff because of its digestible crude fiber and high protein contents. In this study, we obtained a chromosome-scale genome assembly for Paper mulberry using integrated approaches, including Illumina and PacBio sequencing platform as well as Hi-C, optical, and genetic maps. The assembled Paper mulberry genome consists of 386.83 Mb, which is close to the estimated size, and 99.25% (383.93 Mb) of the assembly was assigned to 13 pseudochromosomes. Comparative genomic analysis revealed the expansion and contraction in the flavonoid and lignin biosynthetic gene families, respectively, accounting for the enhanced flavonoid and decreased lignin biosynthesis in Paper mulberry. Moreover, the increased ratio of syringyl-lignin to guaiacyl-lignin in Paper mulberry underscores its suitability for use in medicine, forage, papermaking, and barkcloth making. We also identified the root-associated microbiota of Paper mulberry and found that Pseudomonas and Rhizobia were enriched in its roots and may provide the source of nitrogen for its stems and leaves via symbiotic nitrogen fixation. Collectively, these results suggest that Paper mulberry might have undergone adaptive evolution and recruited nitrogen-fixing microbes to promote growth by enhancing flavonoid production and altering lignin monomer composition. Our study provides significant insights into genetic basis of the usefulness of Paper mulberry in papermaking and barkcloth making, and as forage. These insights will facilitate further domestication and selection as well as industrial utilization of Paper mulberry worldwide.

[Aesthetic evaluation of nasolabial angle alteration on the soft tissue profile of skeleton class I].

OBJECTIVE: To study the influence of nasolabial angle alteration on facial profile attractiveness and investigate the perception differences in profile attractiveness among laypeople. METHODS: A young Chinese female with normal hard and soft tissue cephalometric values was chosen as a research object. Profile photograph was taken in a natural head position. Photoshop software was chosen to rotate the nose tip and upper lip, thus changing the degree and direction of nasolabial angle. A total of 33 different profile pictures were achieved. Thirty-three professional orthodontists and 64 non-professionals were chosen to score these 33 pictures. RESULTS: When the upper lip position was fixed, the profile was considerably attractive because the angle of nasal tip was not changed or altered. When the nasal tip rotation angle was fixed, profiles with a retroclined upper lip were considered significantly attractive by the layperson and professional groups. Regardless of the direction of the nasal tip rotation, the respondents considered the profile with a retroclined upper lip highly attractive. CONCLUSION: The soft tissue profile with a retroclined upper lip looks considerably attractive in Chinese female populations. Therefore, during an orthodontic treatment, appropriate retraction of the incisor is recommended to improve soft tissue profile attractiveness.