Hyperbranched Polyurethane Matrix Research Articles

Hyperbranched Polyurethane‐Supported Pd‐Ag@CQD Nanocomposite: A High Performing Heterogeneous Catalyst

AbstractPolymer nanocomposites designed especially for catalytic application is a relatively unexplored domain in material chemistry as well as synthetic organic chemistry. The current work strives on crafting high performance hyperbranched polymer nanocomposites with catalytic properties for direct organic transformations. Herein, a bio‐derived aliphatic hyperbranched polyurethane (HPU) was fabricated with bimetallic palladium‐silver‐carbon dot (Pd−Ag@CQD) nanohybrid by in situ polymerization technique. Different compositions of the nanocomposite were prepared by varying the loading of nanohybrid. Analytical techniques like FT‐IR, PXRD, TEM, TGA and DSC were utilized for characterization of the nanocomposites. The bimetallic nanohybrid in unison with carbonaceous CQDs was found to be poly‐dispersed in the HPU matrix. The combination of the bimetallic‐cum‐carbonaceous nanohybrid with HPU provided significant improvement of mechanical properties like tensile strength (2.2 fold), elongation at break (1.19 fold), toughness (3.0 fold) etc. over pristine HPU. The bimetallic nanohybrid‐supported nanocomposites also demonstrated vastly enhanced thermal stability (above 300 °C). The nanocomposites demonstrated loading‐dependent enhancement of mechanical and thermal properties. The HPU‐supported Pd−Ag@CQD nanocomposite displayed exceptional efficiency (100% conversions, 30–60 min) as a robust and recyclable catalyst (upto 10 cycles) for rapid oxidative ipso‐hydroxylation of aryl boronic acids to yield corresponding phenols. The poly‐dispersion of Pd−Ag@CQD in HPU offered multiple nano‐reactive sites, while superior mechanical properties of HPU‐supported bimetallic nanocomposites provided stability, heterogeneity and sustainability. The current catalytic protocol presents a facile route for preparation of phenols and its derivatives and can be suitable for opening up new avenues for large‐scale applications.

Smart self-tightening surgical suture from a tough bio-based hyperbranched polyurethane/reduced carbon dot nanocomposite

Design and fabrication of a smart bio-based polymeric material with potent biocompatibility and high performance still remain a challenge in the biomedical realm. In this context, a potential smart suture was fabricated from starch modified hyperbranched polyurethane (HPU) nanocomposites with different weight percentages of reduced carbon dots for the first time. The desired mechanical (tensile strength: 32.14 MPa, elongation at break: 1576% and toughness 439.28 MJ m−3) and thermal (286 °C) attributes of the suture were achieved with 2 wt% of reduced carbon dots in an HPU matrix. The non-contact self-tightening behavior was observed just within 15 s at body temperature of 37 °C ± 1 °C with notable shape fixity (99.6%) and shape recovery (99.7%) effects. The nanocomposites displayed in vitro biodegradability and hemocompatibility. Low lactate dehydrogenase activity and minimal red blood cell lysis indicated the anti-thrombogenicity and anti-hemolytic properties of the nanocomposites. The suitability of the fabricated nanocomposites as a smart biomaterial was supported by the inherent biocompatibility as observed by the growth and proliferation of smooth muscle cells and endothelial cells. Furthermore, they exhibited minimal immunogenic response (TNF α release). Thus, the study paves the way to biodegradable HPU nanocomposites as advanced non-contact triggered rapid self-tightening surgical sutures for biomedical applications.

Fabrication of graphene oxide and hyperbranched polyurethane composite via in situ polymerization with improved mechanical and dielectric properties

Herein, we report a simple and one‐pot route for the synthesis of graphene oxide (GO)/hyperbranched polyurethane (HBPU) composite by in situ polymerization technique. The polyurethane (PU) chains formed covalent linkages with the exposed hydroxyl and carboxylic acid groups on the GO. The composite was characterized by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, and infrared (IR) spectroscopy. The characterization results revealed that the GO sheets were well dispersed within the HBPU matrix, resulting in very good enhancement in tensile strength and Young's modulus of the composites. Differential scanning calorimetry (DSC) suggests that the GO has a nucleating effect for the HBPU. The composites also show a mild increase in stability towards thermal degradation, and significantly, higher dielectric constant compared with neat HBPU at low frequencies. POLYM. COMPOS., 39:2765–2770, 2018. © 2017 Society of Plastics Engineers

Synthesis of click‐coupled graphene sheets with hyperbranched polyurethane: Effective exfoliation and enhancement of nanocomposite properties

ABSTRACTGraphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and 1H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44631.

Nitrogen rich hyperbranched polyurethane‐carbon nanohorn composite: Implications on the development of multifunctional coatings

In the present report, we demonstrate the advantages associated with a multifaceted coating comprising of single‐walled carbon nanohorns (SWNH) and hyperbranched polyurethane (HBPU). To synthesize the HBPU, we utilized sebacic acid and triethanolamine as starting materials employing traditional polycondensation reaction; A3 + B4 approach. The degree of branching as estimated from NMR was found to be ∼60%, indicating a good branching profile. Prepared nitrogen rich HBPU coatings exhibited good corrosion resistance and adhesion to the substrate. Furthermore, an in situ blend of pyrene and functionalized carbon nanohorns (f‐SWNH) were introduced within the HBPU matrix to impart additional properties. The obtained HBPU‐SWNH composites (CNH‐PU) exhibited superior storage modulus (∼1081 MPa), lower corrosion rate (6.16 × 10−5 mm/year), excellent flexibility, and exceptional thermo‐mechanical properties along with fluorescence (due to pyrene moiety). The properties displayed by the composite coatings were much higher as compared to the HBPU in the absence of synergism. POLYM. COMPOS., 39:E772–E779, 2018. © 2016 Society of Plastics Engineers

Mechanical and photothermal shape memory properties of in-situ polymerized hyperbranched polyurethane composites with functionalized graphene

In-situ polymerized hyperbranched polyurethane (HPU) composites with poly(e-caprolactone) (PCL)-functionalized graphene oxide (f-GO) sheets were prepared. Both their mechanical and laser-induced photothermal shape memory properties were investigated and compared with those of GO/HPU composites. The incorporation of f-GO in the HPU matrix significantly improved the mechanical properties of the composites such as the breaking stress, modulus, and elongation-at-break. The f-GO/HPU composites demonstrated an increase of 44 % and 43 % in the breaking stress and modulus, respectively, compared with the HPU. It was also observed that the f-GO/HPU composites demonstrated excellent near-infrared laser-induced shape recovery actuation with an enhanced rate of shape recovery. The improved mechanical and photothermal properties of the f-GO/HPU composites, compared with those of GO/HPU composites, can be attributed to the presence of more interactive sites consisting of HPU molecules with f-GO at the outer surfaces, and an improved dispersion of the graphene sheets in the HPU matrix because of GO functionalization.

Nanocomposites of bio-based hyperbranched polyurethane/funtionalized MWCNT as non-immunogenic, osteoconductive, biodegradable and biocompatible scaffolds in bone tissue engineering.

This study focused on the design of novel mechanically tough, biocompatible, osteoconductive and biodegradable scaffolds based on sunflower oil modified hyperbranched polyurethane (HBPU)/functionalized multi-walled carbon nanotube (f-MWCNT) nanocomposites (NCs), and the response of an animal model on their post-implantation. The NC was prepared by an in situ polymerization technique with different wt% of f-MWCNTs. The tensile strength of the NCs was enhanced to 36.98-47.6 MPa from 23.93 MPa (HBPU) and toughness from 12 767 to 18 427-19 440 due to the addition and efficient dispersion of the f-MWCNTs in the HBPU matrix. The post-60 days in vitro biodegraded NC retained sufficient strength (39 ± 1.65 MPa). The increase in wt% of f-MWCNTs had a significant effect on tailoring the physico-mechanical properties of the polymer. The hematological, histological and immunological indices of toxicity suggested the safety potential of the prepared systems within the tested animal model. Moreover, the cytokines (viz. IL-6 and TNF-α) detection, MTT assay and anti-hemolytic assay boosted the non-toxic behavior of the systems. The NC with interconnected pores size (200-330 μm) showed better proliferation and adherence of osteoblast (MG63) cells compared to the HBPU and the results were comparable with the control. Thus the findings confirmed the non-toxicity of f-MWCNTs in association with the polymer and thereby endorsed the NC as a potential biomimetic scaffold for bone tissue engineering.

Bio-based tough hyperbranched polyurethane–graphene oxide nanocomposites as advanced shape memory materials

A fast and simple approach for the large scale fabrication of highly flexible castor oil-modified hyperbranched polyurethane (HPU)–graphene oxide (GO) nanocomposites with high toughness is reported. Three different wt% (0.5, 1 and 2) of GO are incorporated into a HPU matrix to prepare uniformly dispersed GO-based nanocomposites. The performance studies show a tremendous enhancement of the toughness (2540 to 6807 MJ m−3) as well as the increment of tensile strength (7 to 16 MPa), elongation at break (695 to 810%) and scratch hardness (5 to 6.5 kg) on the formation of the nanocomposites with 2 wt% GO. The Halpin–Tsai model suggests the 3D random distribution of GO in the HPU matrix. Thermal properties such as thermostability, melting point, enthalpy, degree of crystallinity and glass transition temperature (Tg) etc. of the nanocomposites are correlated with their shape recovery (∼99.5%) and shape fixity (∼90%) behaviour. Thus, HPU–GO nanocomposites have the potential to be used as advanced thermo-responsive shape memory materials.

Synthesis of mechanically robust antimicrobial nanocomposites by click coupling of hyperbranched polyurethane and carbon nanotubes

This study demonstrates that mechanically robust antimicrobial nanocomposites of multiwalled carbon nanotubes (MWCNTs) and hyperbranched polyurethane (HBPU) can be prepared via a click chemistry reaction. Various compositions of HBPU-functionalized MWCNTs were synthesized from reactions of azide moiety-containing HBPU with alkyne-functionalized MWCNTs. The HBPU-functionalized MWCNTs were characterized morphologically using transmission electron microscopy and field emission scanning electron microscopy and chemically using Fourier transform infrared spectrometry, Raman spectroscopy, and X-ray photoelectron spectroscopy. The functionalized MWCNTs exhibited excellent dispersion in the HBPU matrix, and as a result, superior mechanical and strong antibacterial properties were obtained. The antimicrobial properties were examined by use of gram-negative bacteria Escherichia coli (E. coli). Consequently the click coupled bonding of MWCNTs with HBPU was very efficient for regulating the composite properties and achieving high performance materials.

Nanostructured hyperbranched polyurethane elastomer hybrids that incorporate polyhedral oligosilsesquioxane

Novel thermoplastic hyperbranched polyurethane (HBP) elastomer hybrids containing polyhedral oligomeric silsesquioxane (POSS) have been synthesized using an A2+B3 approach. Different compositions of these hybrid nanomaterials were obtained from reactions of POSS-diol, triethanolamine, poly(ε-caprolactone)diol, and 4,4′-methylenebis(phenyl isocyanate) with a chain extender. The covalent attachment of POSS molecules to the backbone of the polyurethane chain was characterized with FT-IR and NMR spectroscopies. The non-agglomerated homogeneous dispersion obtained through the covalent attachment of POSS molecules and the HBP matrix was observed by SEM imaging. The mechanical properties, including the tensile and yield strengths, Young’s modulus, and toughness, significantly increased after the introduction of POSS molecules into the hybrids; this increase can be ascribed to the nano-reinforcement effect of the POSS cages and the long-range branched structure of the polymer. Thermogravimetric analyses indicated that the thermal stability of the polymer matrix was improved by the introduction of a small amount of POSS.

Enhanced dispersion of carbon nanotubes in hyperbranched polyurethane and properties ofnanocomposites

Hyperbranched polyurethane (HBPU) nanocomposites with multi-walled carbonnanotubes (MWNTs) were prepared by in situ polymerization on the basis ofpoly(ε-caprolactone)diolas the soft segment, 4,4′-methylene bis(phenylisocyanate) as the hard segment, and castor oil as the multifunctionalgroup for the hyperbranched structure. A dominant improvement in the dispersion ofMWNTs in the HBPU matrix was found, and good solubility of HBPU–MWNTnanocomposites in organic solvents was shown. Due to the well-dispersed MWNTs, thenanocomposites resulted in achieving excellent shape memory properties as well asenhanced mechanical properties compared to pure HBPU.

Synthesis and Characterization of Ag 2S Nanocrystals in Hyperbranched Polyurethane at Room Temperature

Ag 2S nanoparticles in hyperbranched polyurethane matrix were prepared through the in situ reaction with thioacetamide as the sulfur source at room temperature. Transmission electron microscopic analysis revealed a uniform spherical shape for Ag 2S nanoparticles, with an average size of about 4–10 nm and a narrow size distribution. X-ray powder diffraction and UV–vis spectroscopy were also used to characterize the obtained nanoparticles