Dendrimer functionalized polysilane: An efficient and recyclable organocatalyst

Polysilane supported dendrimer was efficiently utilized as an organocatalyst for Knoevenagel condensation reaction. Polysilane support was synthesized by the polymerization of trichloromethylsilane. The polypropyleneimine (PPI) dendrimer was grafted on the polymer support by divergent method. The dendrimer was synthesized up to three generations (G3). The dendrimer functionalized polysilane (PS‐PPIG3) was found to contain high concentration of terminal amino groups. The catalytic activity of the PS‐PPIG3 dendrimer was generalized by conducting the Knoevenagel condensation reaction with diverse sets of substrates, and was found to be an efficient organocatalyst. The condensation product could be easily separated from the reaction medium because of the heterogeneous nature of the polymer support. The reaction conditions were optimized, and the catalyst was found to be reusable. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41593.     

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

The rheological behavior of two series of aliphatic hyperbranched (HB) polyesters, based on 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) and di‐trimethylol propane (Di‐TMP) as a tetrafunctional core, was studied. The effect of the size (pseudo‐generation number, from second to eight) and structure on the melt rheological properties was investigated for a series of hydroxyl‐terminated HB polyesters. In addition, the influence of the nature and degree of modification of the terminal OH groups in a series of fourth‐generation polyesters end‐capped with short and long alkyl chains and some aryl groups on the rheological properties was analyzed. The time–temperature superposition procedure was applied for the construction of master curves and for the analysis of the rheological properties of HB polyesters. The data obtained from WLF analysis of the HB polyesters showed that the values of the thermal coefficient of expansion of free volume α_f and the fractional free volume at the glass transition temperature, f_g, increase with increasing size of the HB polyesters. It was shown that the modified HB polyesters exhibited lower T_g and T_G′=G″ temperatures, above which viscous became dominant over elastic behavior. From an analysis of the master curves of the modified HB polyesters, it was observed that with increasing degree of modification, both storage and loss modules and complex dynamic viscosity and apparent energy for viscoelastic relaxation decrease, because of reduced intermolecular hydrogen interactions. They do not exhibit a plateau of rubbery behavior, which confirms that no entanglements are present and that the molar masses are below the critical molar mass. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41479.     

Synthesis of a branched photosensitive copolymer and its application for negative‐type photoresists

Novel branched copolymers, poly(styrene‐alt‐maleic anhydride) (BPSMA), were synthesized through mercapto chain‐transfer polymerization with styrene, maleic anhydride (MA), and 4‐vinyl benzyl thiol (VBT). Then, the hydroxyl of hydroxyethyl methacrylate was reacted with MA to synthesize branched photosensitive copolymers, p‐BPSMAs. Fourier transform IR spectroscopy and ¹H‐NMR indicated that the synthesis was successful. Gel permeation chromatography indicated that the molecular weight decreased with increasing content of VBT. The thermal properties were characterized by thermogravimetric analysis; the results show that the thermal decomposition temperature of the BPSMAs was greatly enhanced. Real‐time IR was used to evaluate the UV‐curable kinetics of the p‐BPSMAs; the results show that the p‐BPSMAs could rapidly photopolymerize under UV irradiation in the presence of photoinitiators. Moreover, the photoresist based on the p‐BPSMAs exhibited improved photosensitivity when the VBT content increased, and the photoresist with 12 mol % VBT content had a low value of the dose that retained 50% of the original film thickness (10 mJ/cm²), and a 50‐μm resolution could be achieved compared to a linear photoresist. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42838.     

Hyperbranched polyester polyol modified with polylactic acid

In this study the modification of a hyperbranched polyester polyol of second generation (HBP2G) with polylactic acid (PLA) was carried out. The proportions employed of PLA were: 10 (HBP2G90), 25 (HBP2G75), 40 (HBP2G60), and 55 wt % (HBP2G45). The materials obtained were characterized by acid value, hydroxyl value, infrared, nuclear magnetic resonance (NMR), chromatography exclusion size (SEC), dynamic light scattering, thermogravimetric, differential scanning calorimetry, and rheology analyses. The analyses of the acid values and hydroxyl values showed that the reaction between HBP2G and PLA occurred. The greater modification degree was 92.00%. The NMR spectrum shows that evidently the PLA was grafted onto the HBP2G. The SEC analysis revealed that all samples presented values ??of average molecular weight (M_n) and weight average molecular weight (M_w) higher than the HBP2G. The thermal stability of the materials increased with respect to HBP2G and it was independent of the modification degree. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41589.     

Synthesis of blocked and branched waterborne polyurethanes for pigment printing applications

A series of blocked and branched waterborne polyurethanes (BBPUs) have been successfully synthesized and applied in pigment printing of cellulosic substrate. The branched structure was based on an “A₂ + CB₂” approach with diisocyanate prepolymer and diethanol amine. The terminal isocyanate groups were blocked by sodium bisulfite to lower curing temperature and improve the color fastness. The prepolymerization and chain extending could be considered as the end at 70°C after 90 min and at 80°C after another 90 min, respectively. It was suitable for sodium bisulfite to block isocyanate groups at 0°C–5°C for 40 min. The microphase separation of BBPU based on the longest polyethylene glycol (PEG) soft segment appeared. Both curing rate and pencil hardness of BBPU films distinctly reduced as the molecular mass of PEG soft segment ascended. The moisture rate increased from 18.1% to 49.2% with increasing the molecular weight of PEG, indicating that water resistance of the film became poor. Excellent acid and alkali resistances of the BBPU films were obtained. Color fastness to washing, rubbing, and light of the printed cotton fabrics was remarkably enhanced as the BBPU amount ascended to 10% which were cured at 85°C for 6 min. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42780.     

Synthesis of biomimetic hyperbranched zwitterionic polymers as targeting drug delivery carriers

Novel biomimetic hyperbranched copolymers that synthesized by polymerization of zwitterionic monomer (CBB) on the surface of a hyperbranched poly(3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and used as a drug delivery carrier have been investigated by analysis of protein‐adsorption‐resistance, cytotoxicity and cell type‐specific targeting properties. The as‐synthesized biomimetic hyperbranched copolymers showed low toxicity, favorable protein resistant properties and were ultrastable in 100% fetal bovine serum. Folic acid and rodiamin‐B were conjugated to the surface of synthesized micelles to endow it with target drug delivery and fluorescence activity, respectively. Intracellular uptake and in vitro cytotoxicity of HBPO‐poly(carboxybetaine) micelles were investigated. Doxorubicin was used as a model drug for Hela cells during the experiment. All results show that the biomimetic hyperbranched copolymer is a candidate carrier for target drug delivery. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A thiol‐ene clickable hyperbranched polyester via a simple single‐step melt trans‐esterification process

Self‐condensation of AB₂ type monomers (containing one A‐type and two B‐type functional groups) generates hyperbranched (HB) polymers that carry numerous B ‐type end‐groups at their molecular periphery; thus, development of synthetic methods that directly provide quantitatively transformable peripheral B groups would be of immense value as this would provide easy access to multiply functionalized HB systems. A readily accessible AB₂ monomer, namely diallyl, 5‐(4‐hydroxybutoxy)isophthalate was synthesized, which on polymerization under standard melt‐transesterfication conditions yielded a peripherally clickable HB polyester in a single step; the allyl groups were quantitatively reacted with a variety of thiols using the facile photoinitiated “thiol‐ene” reaction to generate a wide range of derivatives, with varying solubility and thermal properties. Furthermore, it is shown that the peripheral allyl double bonds can also be readily epoxidized using meta‐chloroperoxybenzoic acid to yield interesting HB systems, which could potentially serve as a multifunctional cross‐linking agent in epoxy formulations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40248.     

High-toughening modification of polylactic acid by long-chain hyperbranched polymers

The hyperbranched polyester synthesized by “one-step method” was grafted with stearic acid to obtain long-chain hyperbranched polymers (LCHBPs) with a large number of long stearic acid chains at the end. By means of FTIR and ¹³C-NMR characterization, it was proved that stearic acids were grafted onto hyperbranched polyesters (HBPE) to yield LCHBPs successfully. It was determined by GPC and hydroxyl value titration that the number average molecular weight of HBPE was 4.86 × 10³ and the grafting rate of stearic acid was 47%. Polylactic acid (PLA)/LCHBPs blends were prepared by melt processing method. The results showed that comparing with neat PLA, the tensile strength of PLA/LCHBPs blends decreased slightly with the increase of LCHBPs, but still maintained a high level, while the elongation at break and the impact strength of the PLA with 3.0 phr LCHBPs were greatly improved by 1360.0% and 119.8%, respectively. In addition, the impacted fracture characteristics of PLA changed significantly from brittle fracture to ductile fracture after LCHBPs incorporation, with the formation of a large number of filamentous structures. Thus, LCHBPs was an excellent toughening modifier for PLA and the resulting blends with improved performance possess wider applications.     

Facile synthesis of biocompatible polyglycerol hydrogel based on epichlorohydrin

A series of hydrophilic polyglycerol (PG) hydrogel was designed and synthesized via one pot with epichlorohydrin (ECH), H₂O, and NaOH as the starting materials. The equilibrium swelling ratios of PG hydrogels could be tuned by simply changing the feed amount of NaOH. The gels were characterized by carbon nuclear magnetic resonance (¹³C NMR) spectroscopy, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The As‐synthesized PG hydrogels showed temperature‐sensitive swelling behaviors. The results of MTT assay suggested that the PG hydrogels prepared by this novel synthesis method showed comparable cytocompatibility with the recognized poly(ethylene glycol) hydrogel. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43451.     

Performance tuning of glass fiber/epoxy composites through interfacial modification upon integrating with dendrimer functionalized graphene oxide

In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoamine (PAM) dendrimer functionalized graphene oxide (GO) into epoxy matrix. Two different composites each containing varying loading fraction (0.5, 1.0, and 1.5 wt%) of GO and GO-PAM were fabricated via hot press processing. Composites were evaluated for interlaminar shear strength (ILSS), dynamic mechanical properties and thermal conductivity. The inclusion of 1.5 wt% GO-PAM resulted ~57.3%, ~42.7%, and ~54% enhancement in ILSS, storage modulus and thermal conductivity, respectively. Almost, ~71% reduction in coefficient of thermal expansion was also observed at same GO-PAM loading. Moreover, higher glass transition temperature was observed with GO-PAM addition. GO-PAM substantially improved fiber/matrix interfacial adhesion, which was witnessed through scanning electron microscopy. The enhanced thermo-mechanical performance was attributed to interfacial covalent interactions engendered by ring opening reaction between epoxy and amine moieties of PAM dendrimers. These multiscale composites with extraordinary functional properties can outperform conventional counterparts with improved reliability and performance.     

Cyclodextrin‐dendrimer functionalized polysulfone membrane for the removal of humic acid in water

Commercial polysulfone (PSf) membranes were crosslinked with a β‐cyclodextrin‐poly (propyleneimine) (β‐CD‐PPI) conjugate which had β‐CD pendant arms using trimesoyl chloride (TMC) by interfacial polymerization. The morphology and physicochemical properties of the nanofiltration membranes were characterized using Fourier transform infrared/attenuated total reflectance (FT‐IR/ATR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cross‐flow filtration system. Water‐contact angle, water‐intake capacity, and rejection capacities of the membranes were evaluated. The β‐CD‐G4 (generation 4)‐PPI‐PSf and β‐CD‐G3 (generation 3)‐PPI‐PSf membranes both exhibited high humic acid rejection of 72% as compared to the commercial PSf which exhibited 57%. The modified membranes were also more hydrophilic (36° to 41°) than PSf (76°). These results suggest that β‐CD‐PPI nanostructures are promising materials for the synthesis of membranes for the removal of humic acid from water. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4428–4439, 2013     

Nitrile rubber/hindered phenol exterminated hyperbranched polyester materials with improved damping and mechanical performance

Hindered phenol exterminated hyperbranched polyester (mHBP) is fabricated by esterification reaction. The mHBP is introduced into nitrile rubber (NBR) to prepare NBR/mHBP blends. Structure, damping and mechanical properties of NBR/mHBP blends are investigated by Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR, dynamic mechanical thermal analyzer (DMTA), and tensile tester. FTIR spectra of the blends illustrate the intermolecular hydrogen bonding between the NBR and mHBP, contributing to the improvement of damping and mechanical properties. The results indicate that, with the increasing mHBP content, the T_g of the blends shifted to a higher temperature with a broadening temperature range and improved mechanical properties, showing an application in adjusting the T_g and temperature range without decreasing of loss factor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42605.     

Functional Dendritic Polymers for the Development of Hybrid Materials for Water Purification

Dendritic polymers can, depending on their polarity and the interaction ability of their interior, encapsulate water contaminants. By appropriate functionalization of their external groups and following integration with ceramics, hybrid devices bearing nanosized sorbents are developed. In a first strategy, hydrophobic dendritic polymers were non‐covalently attached on the surface of ceramic filter modules, while in a second, dendritic polymers were covalently bound on these surfaces. In another method, dendritic polymers act as templates and induce the formation of silica/dendritic polymer nanospheres. In all cases, the property of dendritic polymers to encapsulate impurities remains intact, leading to effective filtration/purification systems.

     

Thiol-terminated hyperbranched polymer for DLP 3D printing: Performance evaluation of a low shrinkage photosensitive resin

In order to lower the volume shrinkage of the DLP 3D printing photosensitive resins during printing, a thiol-terminated hyperbranched polymer (T-HBP) was synthesized and introduced into the bisphenol A epoxy acrylate (EA) based photosensitive resin system. The obtained T-HBP was characterized by FTIR and ¹H NMR spectra, and the grafting rate of sulfhydryl was determined. The mechanical properties of the photosensitive resins were measured by tensile and impact strength measurement. The glass transition temperature of the photosensitive resins was analyzed by DSC and the impact fracture surface was observed by SEM. T-HBP exhibited a much lower viscosity than its linear counterparts, and the addition of thiol improved the curing speed of the photosensitive resins. When the amount of T-HBP added was 20 wt%, the shrinkage of the photosensitive resins was reduced by about 45.5% and the impact strength increased by 33.9% compared with the control. The macromolecular spherical structure of T-HBP effectively reduced the functional group density of the photosensitive resins. In addition, the thiol-acrylate photopolymerization introduced by T-HBP further reduced the volume shrinkage of the photosensitive resins.     

Lipase-catalyzed synthesis of hyperbranched polyester improved by autocatalytic prepolymerization process

This work developed a facile and environmentally friendly route for lipase-catalyzed synthesis of a hyperbranched polyester by introducing an autocatalytic prepolymerization of comonomers. Trimethylolpropane, 1,8-octanediol, and adipic acid as comonomers for synthesizing the hyperbranched polyester were first prepolymerized via the automatic catalytic effect of the reactants themselves to obtain an appropriate reaction substrate for further lipase-catalyzed polymerization, where immobilized lipase Novozym 435 was used as a biocatalyst. The acidity and fluidity of optimized oligomers after the autocatalytic prepolymerization provide a benign reaction substrate for the retention of enzymatic activity in the subsequent lipase-catalyzed esterification, which is crucial for the enzymatic polymerization. The optimum reaction temperature and reaction time for prepolymerization were determined to be 120 °C and 150 min. The molecular weight (M _w) of the prepared polyester was approximately 26,300 g/mol. Quantitative analysis of ¹H-NMR and inverse-gated ¹³C-NMR spectra confirmed the hyperbranched structure of the resulting polyester with a branching degree of 31.3%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47221.     

Effect of generation number on properties of fluoroalkyl-terminated hyperbranched polyurethane latexs and its films

The 1–3 generations of hyperbranched polyesters (HBPE-1/2/3) were synthesized from trimethylolpropane (TMP) and 2,2-dimethylol propionic acid (DMPA) by “quasi-one-step method.” Then, isophorone diisocyanate (IPDI), polybutylene adipate (CMA-1044), DMPA and 1,4-butanediol (BDO) were utilized to prepare the urethane prepolymer (PU), which was reacted with HBPE to synthesize hyperbranched polyurethanes (HBPU). Finally, 1–3 generations of fluoroalkyl-end-capped hyperbranched polyurethanes (FHBPU) latexes were obtained by the reaction of perfluorohexyl ethanol (S104) and HBPU as well as the self-emulsification process. Structure of the products, the properties of different FHBPU emulsions and its films were investigated by FTIR, ¹H NMR, TEM, DLS, TGA, XPS, XRD, SEM, AFM and static contact angle measuring instrument. Results showed that the particle size of FHBPU latexes increased gradually with the increase of generation number. SEM and XRD results verified that an amount of the crystal particles was increased with the increase of generation number. XPS and AFM demonstrated that degree of microphase separation and film roughness was increased with the increase of branching degree. Static water contact angles could attain 95.9°, 100.3°, and 107.0°, respectively on the 1–3 generations of FHBPU films, compared to that on PU (75.1°).     

Synthesis of hyperbranched polybenzoxazoles and their molecular composites with epoxy resins

Hyperbranched aromatic polymers have attracted great attention recently because they combined the processability of hyperbranched polymers and the high‐level performance of aromatic polymers. Here, a one‐pot strategy for the synthesis of hyperbranched Polybenzoxazoles (HBPBOs) by polycondensation of 2,2‐Bis (3‐amino‐4‐hydroxyphenyl) hexafluoropropane and 1,3,5‐benzenetricarboxylic acid in Polyphosphoric acid was reported. The HBPBOs exhibited good solubility in organic solvents because of the branched structure and the flexible hexafluoropropane groups in main chains. The structure and terminal functional groups could be tailored by adjusting the molar ratio of two monomers. FT‐IR, NMR and XRD measurements confirmed the structure of HBPBOs, while thermogravimetric analysis (TGA), UV‐vis, and photoluminescence spectra, combined with the comparison with linear PBOs demonstrated the intriguing optical properties and good thermal stabilities of HBPBOs. The good solubility of HBPBOs also permitted their usage as molecular reinforcement for polymer composites as demonstrated in this study of HBPBOs/epoxy composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41942.     

Synthesis of hyperbranched polymers by free radical addition‐coupling polymerization with A3/B2 and A2A′/B2 approaches

Two tribromide compounds, 1,3‐(propanoic acid, 2‐bromo‐)‐2‐(2‐bromo‐1‐oxopropylamino)propyl ester (A 1 ) and trimethylolpropane tris(2‐bromopropionate) (A 2 ), were synthesized. By Cu/N,N,N′,N′,N″‐pentamethyldiethylenetriamine (PMDETA)‐mediated radical addition‐coupling polymerization (RACP) of 2‐methyl‐2‐nitrosopropane (MNP) with the tribromide compounds, two types of hyperbranched polymers were synthesized under mild conditions, respectively. Polymerization degrees of the polymers increased with time gradually, which is in line with a step‐growth polymerization mechanism. By tracing the polymerization process by gel permeation chromatography and NMR analysis, proper reaction conditions to get hyperbranched polymers was obtained. Based on the results of NMR analysis on the polymer chain structure, mechanism of forming hyperbranched polymer has been proposed, which includes formation of carbon radicals from the tribromo monomer through single electron transfer, their reaction with MNP to form nitroxide radicals, and cross‐coupling reaction of the nitroxide radicals with other carbon radicals. The gelation point of the A 2 ‐MNP system is larger than that of the A 1 ‐MNP system, indicating that probability of intramolecular cyclization in A 2 ‐MNP RACP system is higher than the A 1 ‐MNP system. The reactivity of —NHCOCH(CH₃)Br group of A 1 is lower than its two —OCOCH(CH₃)Br groups, and this resulted in longer distance between two adjacent branch points in the hyperbranched polymer of A 1 ‐MNP than the A 2 ‐MNP system. It is possible to adjust the chain structure of RACP‐based hyperbranched polymer by changing the reactivity of the functional groups in A₃ monomer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41972.     

Crystallization behavior of hyperbranched polyethylenes with different degree of branching

Hyperbranched polyethylenes (HBPEs) with different degree of branching (DB) and similar M_n are used to investigate the effect of branch structure on their crystallization behaviors. The crystal structure, isothermal, and non‐isothermal crystallization kinetics of HBPEs are studied by X‐ray diffraction and differential scanning calorimetry. The isothermal crystallization process is analyzed by the Avrami equation while the non‐isothermal crystallization process is analyzed through the Ozawa and Mo methods. The XRD results indicate that the crystallization ability of HBPEs is weakened with the introduction of branch structure, i.e., the crystallinity of HBPEs decreases with the increase of DB, and even tends to zero. The kinetics results of isothermal and non‐isothermal crystallization verify the peculiar effects of DB on the crystallization process of HBPEs. In detail, a little of branch structure can accelerate the crystallization process of HBPEs, however a large number of branch can inhibit it. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44127.     

Surface properties and biocompatibility of cellulose acetates

The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012