Supramolecular polycaprolactone nanocomposite based on functionalized hydroxyapatite

A well-defined quadruple hydrogen bonding strategy involving dimerization of 2-ureido-4[1H]-pyrimidone (UPy) units is innovatively designed to prepare polyureas with high overall mechanical properties. Three polyureas containing different amounts of UPy units were synthesized by replacing a portion of isophorone diisocyanate (IPDI) with a UPy-derived diisocyanate. The formation of quadruple hydrogen bonds in hard segments via UPy dimers was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the polyureas were evaluated by uniaxial tensile testing. Compared to the polyurea without UPy units, remarkable improvements in Young’s modulus, tensile strength, and toughness were simultaneously achieved when UPy units were incorporated. The mechanism behind the strong strengthening effect rooted in the stronger intermolecular forces among hard segments brought by the quadruple hydrogen bonds, which were stronger than the inherent bidentate and monodentate hydrogen bonds among urea groups, and the slower soft segmental dynamics reaveled by both increased Tg and relaxation time of the soft segments. The mechanism behind the strong toughening effect was ascribed to more effective energy dissipation brought by the quadruple hydrogen bonds that served as stronger sacrificial bonds upon deformation. This work may offer new insight into the design of polyurea elastomers with comprehensively improved mechanical properties.

One of the goals of tissue engineering is to create composites that can mimic the behavior of bone in terms of various properties and lead to faster healing with minimal side effects. In this regard, in the present study, porous nanocomposite scaffolds based on Poly(Xylitol-Dodecanedioic acid) (PXDDA) and polycaprolactone (PCL) were prepared in the presence and absence of hydroxyapatite (HA) nanoparticles (NPs) using a salt leaching method with sodium chloride as porogen particles. The results of microscopic examination showed that the presence of HA NPs significantly increased the porosity of the polymer-based scaffold and contact angle (CA) tests showed that these NPs greatly improved the hydrophilicity of the samples. In addition, element mapping and XRD analyses indicated good dispersion of the HA NPs in the polymer matrix. The FTIR results also showed that the sample containing 70% PXDDA and 30% PCL with HA NPs had the highest hydroxyl, hydrocarbon, and ester linkages. In addition, compression tests and dynamic mechanical analysis (DMA) showed that the inclusion of the NPs weakened the mechanical properties of the nanocomposite produced. In addition, the results of the MTT test showed that the presence of HA NPs in this polymer matrix reduced toxicity and increased cell viability.

A facile method for preparing supramolecular waterborne polyurethane (WPU) based on quadruple hydrogen bonds (4H‐WPU) is reported. Herein, 4H‐WPU with quadruple hydrogen bonds in main chain were synthesized by poly (1,4‐buthylene‐neopentylene adipate glycol) as soft segment, 2‐ureido‐4[1H]‐pyrimidinone (UPy) functionalized monomer, isophorone diisocyanate, 2,2‐Bis(hydroxymethyl)propionic acid (hydrophilic monomer), isophorondiamine, triethylamine (neutralizer), and monoethanolamine (blocking agent) as hard segment. The molecular weight of 4H‐WPU was controlled around 18,000 consistently. The properties of 4H‐WPU with different content of hydrophilic group, hard segment, and UPy units were characterized and the results could provide the reference for preparing supramolecular WPU with high mechanical and self‐healing performance while maintaining dispersion stability. The tensile strength of 4H‐WPU was 10 times of the blank sample. The healing time of scratched 4H‐WPU film was inversely proportional to the content of UPy‐ functionalized monomer and the shortest healing time is 2.5 hr at 80°C. Mechanical performance of healed films can be restored to more than 90%.

It is still challenging and attractive to prepare polyurethane (PU) materials with excellent self-healing ability while improving their mechanical properties and high ductility. Here, a multifunctional linear PU supramolecular elastomer was successfully prepared by introducing a cross-linking network of quadruple hydrogen bonds and thermo-reversible Diels–Alder bonds and rigid ring structure to the linear backbone. The results exhibited that the obtained PU elastomer displayed a high tensile strength (6.30 MPa), elongation (1957.84%), toughness (84.48 MJ/m3), and excellent repair efficiency (93.33%). The quadruple hydrogen bonds from 5-(2-hydroxyethyl)-6-methyl-2-aminouracil and thermo-reversible Diels–Alder bonds from the conjugated reaction of 4,4′-bismaleimide diphenylmethane with furfuryl alcohol, due to its synergetic dual reversible bonds, formed the PU elastomer that possessed excellent mechanical, self-healing, shape recovery, and reprocessing properties. The prepared multifunctional PU can be used as a substrate for flexible conductive materials or as conductive composite material with conductive materials, which can self-repair many times when the surface is damaged, can be recycled, and greatly improve the service life of the material. Therefore, the prepared multifunctional high-performance self-healing PU materials have potential applications in several fields.

Shape memory and self-healing properties of polymer-grafted Fe3O4 nanocomposites implemented with supramolecular quadruple hydrogen bonds

Nuclei are often under external stress, be it during migration through tight constrictions or compressive pressure by the actin cap, and the mechanical properties of nuclei govern their subsequent deformations. Both altered mechanical properties of nuclei and abnormal nuclear morphologies are hallmarks of a variety of disease states. Little work, however, has been done to link specific changes in nuclear shape to external forces. Here, we utilize a combined atomic force microscope and light sheet microscope to show SKOV3 nuclei exhibit a two-regime force response that correlates with changes in nuclear volume and surface area, allowing us to develop an empirical model of nuclear deformation. Our technique further decouples the roles of chromatin and lamin A/C in compression, showing they separately resist changes in nuclear volume and surface area, respectively; this insight was not previously accessible by Hertzian analysis. A two-material finite element model supports our conclusions. We also observed that chromatin decompaction leads to lower nuclear curvature under compression, which is important for maintaining nuclear compartmentalization and function. The demonstrated link between specific types of nuclear morphological change and applied force will allow researchers to better understand the stress on nuclei throughout various biological processes.

In composites of hydroxyapatite (HA) nanoparticles with a polymer matrix, the aggregation of nanoparticles would induce structural defects. In order to improve the dispersibility of HA nanoparticles in poly(ethylene glycol) dimethacrylate (PEGDMA) matrix and enhance mechanical properties of the HA/PEGDMA composite as potential bone substitute material, surface‐grafted HA nanoparticles with poly(ethylene glycol) monomethacrylate (PEGMA) were prepared, and crosslinked with PEGDMA under UV light to form a composite. The structure of HA‐g‐PEGMA was characterized by X‐ray diffraction (XRD) and thermal gravimetric analysis (TGA). The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) was evaluated by SEM. The mechanical properties of the composites were investigated by compressive test. The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) matrix was better than the bare HA. At a 1 wt % content of loading, the strength of composites increased by 14%, and the modulus increased by 9%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A series of poly(lactide) (PLA)‐based supramolecular polymers based on linear PLLA‐b‐PCL‐b‐PLLA triblock copolymers (PLLA, poly(l‐lactide); PCL, poly(ε‐caprolactone)) or/and three‐arm star (PCL‐b‐PDLA)3 block copolymers (PDLA, poly(d‐lactide)) were synthesized. The effects of the structure and composition on crystal structure, crystallization behavior, spherulite morphology and mechanical properties of the synthesized supramolecular polymers were investigated. The results of DSC and polarized optical microscopy indicated that the supramolecular polymer exhibited poor crystallization ability with respect to PCL/PLA block copolymer, and the crystallinity of the supramolecular polymer with alternating PCL/PLA multiblock structure was stronger than that with similar crosslinked network structure. The presence of molten PCL blocks disturbed the orientation of lamellae, forming spherulites with feather‐like dendrites, and ring‐banded spherulites were observed as the molecular weight of the PLA blocks increased. The results of tensile tests demonstrated that supramolecular polymers with larger molecular weight of PLA blocks showed the pronounced ductile fracture. On this basis, stereocomplexed supramolecular polymers were also synthesized, and it was found that the stereocomplex crystals had a significant impact on the crystallization and mechanical properties of the supramolecular polymers. Therefore, in this work a novel technique for manufacturing toughened PLA‐based material and tuning its performances is proposed, which may promote the application of PLA‐based materials in more fields. © 2022 Society of Industrial Chemistry.

Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy

Toughening diene elastomers by strong hydrogen bond interactions

Being a key player in intercellular communications, nanoscale extracellular vesicles (EVs) offer unique opportunities for both diagnostics and therapeutics. However, their cellular origin and functional identity remain elusive due to the high heterogeneity in their molecular and physical features. Here, for the first time, multiple EV parameters involving membrane protein composition, size and mechanical properties on single small EVs (sEVs) are simultaneously studied by combined fluorescence and atomic force microscopy. Furthermore, their correlation and heterogeneity in different cellular sources are investigated. The study, performed on sEVs derived from human embryonic kidney 293, cord blood mesenchymal stromal and human acute monocytic leukemia cell lines, identifies both common and cell line-specific sEV subpopulations bearing distinct distributions of the common tetraspanins (CD9, CD63, and CD81) and biophysical properties. Although the tetraspanin abundances of individual sEVs are independent of their sizes, the expression levels of CD9 and CD63 are strongly correlated. A sEV population co-expressing all the three tetraspanins in relatively high abundance, however, having average diameters of <100 nm and relatively low Young moduli, is also found in all cell lines. Such a multiparametric approach is expected to provide new insights regarding EV biology and functions, potentially deciphering unsolved questions in this field.

Objective: to assess the effect of different filler loading on the fracture resistance of CAD/ CAM composite inlays when restoring MOD cavity in premolar teeth. Materials and methods:A two type of CAD/CAM resin composite block with different amount of filler loading were used in this study as the follow: Grandio Bloc with high filler loading (HFL) about 86% filler and BRILLIANT Crios with low filler loading (LFL) about 70% filler.A 40 maxillary premolar were divided equally into four main groups (10 teeth each); a positive control group of unprepared teeth and a negative control group with prepared and unrestored MOD cavity.While the two other restored groups in which teeth with prepared MOD cavities were restored either with the high filler loading Grandio Bloc CAD/CAM resin composite inlay or low filler loading BRILLIANT CAD/CAM resin composite blocks.A standardized MOD cavity were prepared in premolar teeth using the inlay preparation kit.working and master models were fabricated.A new restoration was created in the Cerec in-lab software version.The restoration were processed and cemented in place using Dual-link universal Resin cement.All specimen groups (positive control, negative control and restored groups) were tested for fracture resistance using universal testing machine.Fractured teeth were examined with USB digital microscope at 25X magnification.Twoway ANOVA (Analysis of Variance) was used to compare between groups.Tukey's post-hoc test was used for pair-wise comparison between the mean when ANOVA value were significant.The significance level was set at P≤0.005.Results: There was no statistical significant difference between the intact teeth group and HFL GRANDIO inlays and LFL BRIILIANT CRIOS.However there were statistically significant between prepared but not filled teeth groups and all other groups.The HFL GRANDIO inlays restored teeth group recorded high mean value than LFL BRIILIANT CRIOS but without statistically significant difference between them.A mixed type of failure was detected; cohesive failure either within tooth and restoration and adhesive failure along cement line.

This research explores the correlation between the structural properties of supramolecular biocomposites and their mechanical strength. Hybrid biocomposites composed of surface-modified hydroxyapatite nano-particles and supramolecular polycaprolactone (SP PCL), were prepared at different compositions, and their mechanical, thermal and viscoelastic properties as well as biodegradability, biocompatibility and cytotoxicity were evaluated in vitro. The results were compared with those for SP PCL/naked hydroxyapatite nano-composites. We show that surface modification of hydroxyapatite nanoparticles resulted in outstanding improvement of tensile strength and modulus up to 3.6 and 2.2-fold, respectively. At above 10 wt% HAp and 20 wt% HApUPy, heterogeneous nano-composites with inferior mechanical properties were obtained. Based on rheological (in steady shear mode) and small/wide angle X-ray scattering measurements, unusual improved mechanical properties were ascribed to the formation of supramolecular clusters around nanoparticles. In-vitro degradation of the supramolecular nano-composites was also studied to investigate the overall product biodegradation as well as toxicity of the degradation product(s).

Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced chlorosulfonated polyethylene (CSM) composites were used to study their relaxation behavior as a function of temperature and frequency, respectively. A marginal increase in glass transition temperature has been observed upto 30 phr carbon black filled polymer composite, beyond which it decreases, which has been explained on the basis of aggregation of filler particles in the polymer matrix. The strain dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.1–200%. The nonlinearity in storage modulus increases with increase in filler loading. It can be explained on the basis of filler–polymer interaction and aggregation of the filler particulates. The frequency dependent dynamical mechanical analysis has also been studied at frequency range of 0.1–100 Hz. The variation in real and complex part of impedance with frequency has been studied as a function of filler loading. The effect of filler loading on ac conductivity has been observed as a function of frequency. An increase in conductivity value has been observed with increase in filler loading. This can be explained on the basis of formation of conducting paths between filler particulates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Model of transport in microcrystalline silicon