Thermally Reversible Crosslinked Polyurethanes Based on Blocking and Deblocking Reaction

New self‐healing crosslinked bisphenol‐S polyurethane (BPS/PU) including thermal reversible urethane bonds is prepared to balance the mechanical and self‐healing properties. BPS/PU is synthesized with BPS as chain extender to improve the mechanical property in the effect of high molecular regularity of BPS and extra stronger physical crosslinking in BPS/PU. The crosslinked structure of BPS/PU is confirmed by Fourier transform infrared spectra and swelling‐dissolution test. BPS/PU demonstrates great thermal reversability after three heating and cooling cycles and exhibits shorter relaxation time (3.3 min). The tensile strength and the tensile elongation of BPS/PU are up to 14.54 MPa and 877.12%, respectively, which are much higher than the value reported in literature. The qualitative self‐healing analysis of BPS/PU confirms that the cracks can be healed largely after healing progress, and the quantitative self‐healing analysis exhibits great healing properties with the healing efficiency of up to 77.92%.     

Synthesis and Characterization of Novel Colored Polyurethanes

ABSTRACT

Azo disperse dyes containing N, N-diethylol group have been prepared and each dye was polycondensed with 4,4′ -Diphenyl methane diisocyanate. The resultant colored polyurethanes were characterized by nitrogen content, IR spectral studies, number average molecular weight ([Mbar]n), estimated by conductometric titration, and thermogravimetry. The electrical conductivity of all the polyurethanes was measured at room temperature.     

Synthesis of Y-type Polyurethanes Containing Novel NLO Chromophore

Novel nonlinear optical chromophore with strong electron donor and isolation groups on both sides were synthesized and characterized by mass spectrum and hydrogen nuclear magnetic resonance. Electro-optical polymers with different chromophore loading densities were prepared and showed us good thermal stabilities, all of their thermal decomposition temperature were higher than 250°C. Large EO coefficients were also obtained by second harmonic generation method 29, 47, and 72 pm/V for PU-C10, PU-C15, and PU-C20, respectively. Solvatochromism of polymer PU-C10 was also studied; the result indicated us that this kind of polymers could be used as solvent polarity indicator material.     

Re-Mendable Polyurethanes

Novel re-mendable polyurethanes were prepared by the Diels-Alder cycloaddition reaction of urethane bismaleimides to bisfuryl monomers. The urethane bismaleimides were synthesized by an addition reaction of 4-maleimidophenylisocyanate to macrodiols, such as polycaprolactone diol (M_n ? 1250 and 2000), PEA-2000 and PBA-2000. The bisfuryl monomers were obtained by the reaction of 2-furfuryl alcohol with hexamethylene diisocyanate or by open-ring reaction of the oxirane ring from diglycidyl bisphenol A with furfuryl amine.     

Development of Novel Iron Crosslinked CMC Nanoadsorbents for the Remediation of Arsenic Ions

Iron crosslinked carboxy methyl cellulose (CMC) nanoparticles prepared by the process of emulsion crosslinking were studied for the removal of arsenic(V) ions from aqueous solution. Batch and column studies were conducted in order to investigate the efficiency of nanoparticles towards arsenic remediation. The Langmuir and Freundlich equations were applied to describe the biosorption isotherm. The results obtained from fixed bed studies showed that the column demonstrates fairly well at lowest flow rate and also, bed exhaustion time was found to increase with increasing bed height. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. Antibacterial studies were also conducted which confirms that Fe-CMC nanoparticles are efficient towards the removal of bacteriological contamination also.     

阻燃型可生物降解聚氨酯

通过对淀粉的磷酸酯化改性,并以磷酸酯化淀粉为反应性阻燃剂,合成出既具生物降解特性,又具阻燃特性的聚氨酯弹性片材,为开拓聚氨酯“绿色”产品探索新的途径。     

Novel Side‐Chain Dendritic Polyurethanes Based on Hydrogen Bonding Rich Polyurea/Malonamide Dendrons

Summary: Hydrogen bonding rich polyurea/malonamide dendrons have been utilized as building blocks for the synthesis of novel SCDPUs. The resulting microstructure of soft‐rich domains reinforced by these side chain rigid dendritic domains via strong hydrogen bonding interactions was explored for these segmented polyurethanes. DSC and FT‐IR results indicate that certain degrees of phase separation are present between rigid dendritic structures and soft PTMO domains. The phase separation structures are in the order of 100 nm based on the results of AFM and SAXS. The tensile measurements show that the incorporation of dendritic side chain structures as the hard segments can enhance the mechanical properties of these fabricated polymers.

AFM phase image and chemical structure for the side chain dendritic polyurethane.     

Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant Binders

Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4‐butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co‐polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption‐rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265∼270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (<393 K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion.     

水性聚氨酯乳液的研究新进展

介绍了聚氨酯的发展历史,详细阐述了水性聚氨酯的制备研究与应用现状,并阐述了水性聚氨酯在改性及应用方面的新进展.     

Polyurethanes and polyesters from lignin

Lignin, obtained through steam explosion from straw, was completely characterized via elemental analysis, gel permeation chromatography, ultraviolet and infrared spectroscopy, and ¹³C and ¹H nuclear magnetic resonance spectrometry. Polyurethanes were obtained by treating steam‐exploded lignin from straw with 4,4′‐methylenebis(phenylisocyanate), 4,4′‐methylenebis(phenylisocyanate) –ethandiol, and poly(1,4‐butandiol)tolylene‐2,4‐diisocyanate terminated. The obtained materials were characterized by using gel permeation chromatography, infrared spectroscopy, and scanning electron microscopy. Differential scanning calorimetry analysis showed a T_g at ?6°C, assigned to the glass transition of the poly(1,4‐butandiol) chains. The presence of ethylene glycol reduced the yields of the polyurethanes. The use of the prepolymer gave the best results in polyurethane formation. Steam‐exploded lignin was used as the starting material in the synthesis of polyesters. Lignin was treated with dodecanoyl dichloride. The products were characterized by using gel permeation chromatography, infrared spectroscopy, ¹³C and ¹H nuclear magnetic resonance spectrometry, and scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1451–1456, 2005     

Polyurethanes derived from coal extract

Subbituminous coal from the powder river basin was extracted with N,N-dimethylformamide at atmospheric pressure to yield a solid extract that provided phenolic and carboxylic acid groups. The coal extract was employed as polyol in polyurethane (PU) synthesis. A solvent-free synthesis using 2,4-toluene diisocyanate (TDI) resulted in a porous PU solid. Reaction with TDI in solution resulted in a soluble PU that could be applied as adhesive or coating. Coatings were also prepared from coal extract solutions and commercial, polymeric isocyanates, providing excellent adhesion to aluminum. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48776.     

Synthesis of L-Lactide-Based Segmented Polyurethanes

A series of segmented polyurethanes with polylactidediols soft segments and methylene-diphenyl-diisocyanate/1,4-butanediol hard segments with molecular weights in the range of 6.18 × 10³ to 9.36 × 10³ Da were synthesized. Stannous octoate was the catalyst for the reactions. These polymers were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, gel permeation chromatography, and thermogravimetric analyzer. Fourier transform infrared analyses revealed the formation of urethane groups and complete curing of polyurethane. The thermal degradation temperatures were in the range of 248.55–257.09°C. X-ray diffraction studies confirmed the segmented structure of polyurethanes.     

Polyurethanes having shape memory effects

Segmented polyurethanes (PUs) were prepared from polycaprolactone diols (PCLs), 4,4′-diphenylmethane diisocyanate, and 1,4-butanediol, and tested for shape memory effects. Effects of soft segment molecular weight (M_n = 2000, 4000 and 8000), soft segment content (50–90%), and maximum strain (_m = 100, 200, and 600%) on the cyclic tensile properties as well as the dynamic mechanical, and mechanical properties below (25°C) and above (65°C) the shape recovery temperatures were studied. With increasing soft segment contents: i) glassy state modulus increased and rubbery state modulus decreased; ii) hardness increased at room temperature, and decreased at 65°C; iii) recovery strain decreased with PCL 2000, and increased with PCL 8000 based PUs. On the other hand, the increase in soft segment length resulted in: i) increased rubbery state modulus as well as glass state modulus; ii) increased hardness at room and high temperatures; iii) increased recovery strain at high soft segment content. Tensile yielding became clear with increasing soft segment length and content. Strain upon cooling and unloading (_u) and residual strain (_p) increased, and recovery strain (_r) decreased with cycling. Among these, residual strain was most sensitive to the cycling. Most of the cycling effects were confined during the first one or two cycles. These results were interpreted in terms of soft segment-hard segment phase separation and soft segment crystallization.     

Short-chain phorbol ester constituents of croton oil

Five phorbol diesters, three 4-deoxy-4α-phorbol diesters, two phorbol monoesters, and one 4-deoxy-4α-phorbol monoester were isolated from a commercial sample of croton oil and characterized spectroscopically. Their purification was achieved using combinations of droplet countercurrent chromatography, low-pressure column chromatography over phase-bonded silica gel, and preparative thin layer chromatography. All of these isolates were shown to possess short-chain ester functionalities, with 12-O-tiglylphorbol-13-isobutyrate, 12-O-(2-methyl)butyrylphorbol-13-isobutyrate, 12-O-(2-methyl)butyrylphorbol-13-acetate, 12-O-tiglyl-4-deoxy-4α-phorbol-13-isobutyrate, 12-O-tiglyl-4-deoxy-4α-phorbol-13-acetate, 12-O-(2-methyl)butyryl-4-deoxy-4α-phorbol-13-acetate, phorbol-12-tiglate and 4-deoxy-4α-phorbol-13-acetate being new compounds. A contribution from the Program for Collaborative Research in the Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago.     

Crosslinked polymer nanocapsules

Polymer nanocapsules (PNCs) are an important class of nanocarriers, but applications of conventional non‐crosslinked PNCs have been significantly limited because they are susceptible to environmental conditions. Synthesis and applications of crosslinked PNCs (CPNCs) with robust covalently stabilized nanostructures have attracted great interest over the past decade. Three major categories of template synthesis approaches for the preparation of CPNCs have been established: (1) cavitation of shell‐crosslinked nanostructures, (2) vesicle‐based crosslinking and (3) emulsion interfacial crosslinking. This article provides a critical and comprehensive review of these approaches. Several special cases of the synthesis of CPNCs are also reviewed. © 2016 Society of Chemical Industry     

形状记忆聚氨酯研究现状

本文在介绍形状记忆聚氨酯的形状记忆机理及其影响因素的基础上,介绍了交联型形状记忆聚氨酯、复合改性形状记忆聚氨酯以及水性形状记忆聚氨酯的国内外研究进展,并简要介绍了形状记忆聚氨酯在纺织、医疗等方面的应用,最后对形状记忆聚氨酯的发展方向进行了展望。     

非异氰酸酯聚氨酯的制备与应用

非异氰酸酯聚氨酯在制备过程中避免了高毒性且对湿气敏感,具备优良的力学性能、热性能和施工性能。介绍了非异氰酸酯聚氨酯的合成原理、性能和应用,对其应用领域和前景进行了展望。