Preparation of gelatin/polyoxypropylene grafted copolymers by isocyanate promoted “grafting onto” reaction

A “grafting onto” method for the synthesis of protein-based grafted copolymers is here described. Monofunctional oligo(oxypropylene) chains carrying a terminal isocyanate group were prepared and coupled with gelatin likely by reaction with hydroxyl or primary amino groups. A grafting yield higher than 85% was obtained by using an amount of isocyanate terminated oligo(oxypropylene) of 0.2 mmol per gram of gelatin. A tailored purification procedure based on fractionation with selective solvents was set up to remove homo-coupling products, affording water soluble gelatin-oligo(oxypropylene) graft copolymers having up to 19% wt of grafted oligo(oxypropylene) chains, as indicated by elemental analysis. The composition of all sample fractions were accomplished through NMR, FT-IR and elemental analysis. A negligible insoluble fraction and a water soluble gelatin fraction having a higher modification degree were obtained when the unreacted 1,6-diisocyanatehexane was removed by distillation from the intermediate reagents.The solid films of the graft copolymers showed single-phase morphology by scanning electron microscopy (SEM) observation, confirming the covalent bond formation between oligo(oxypropylene) and gelatin. Simple oligo(oxypropylene)/gelatin blends were prepared and characterized by SEM and stress-strain measurements for comparison.     

Diamine-catalyzed urethane reaction of 1,3-propanediol with phenyl isocyanate

The urethane reaction of 1,3-propanediol with phenyl isocyanate is monitored by means of in situ FTIR. 1,4-Diazabicyclo[2.2.2]octane (DABCO) and N,N,N′,N′-tetramethylethane-1,2-diamine (TMEDA) are used as catalysts. Reaction rates are calculated, and reaction kinetics are studied. Furthermore, Gaussian programs are used to calculate steric configuration and electronegativity of those two diamines. The electronegativity of TMEDA is greater than that of DABCO, but the steric hindrance of DABCO in nitrogen atom is smaller. Steric hindrance plays a more important part in reaction kinetics, which makes the reaction to be catalyzed by DABCO at a faster rate. Finally, activation energy, activation enthalpy, and activation entropy for the reaction are calculated, followed by the discussion of reaction mechanism.     

相转移催化法NaHSO3封闭异氰酸酯反应速率的研究

以亚硫酸氢钠固体粉末为封闭剂,丙酮为溶剂对多亚甲基多苯基异氰酸酯（PAPI）进行封闭反应。考查了在不同温度下异氰酸根浓度（-NCO％）随时间变化的情况,并进行了动力学分析,计算出不同温度下的反应动力学常数。     

封端异氰酸酯的制备及其解封研究

用甲乙酮肟(MEKO)对端NCO预聚体进行封端,考查了不同的封端率对端NCO预聚体黏度的影响.用TGA、DSC、TG-IR等对封端聚氨酯解封过程进行研究.实验结果表明,当封端聚氨酯中残余NCO%低于0.1%时,贮存期可达1年以上.H'NMR分析表明,端异氰酸酯封闭成功.MEKO封端的聚氧酯在105℃解封,与聚醚胺混合后...     

Microwave-assisted reaction of gelatin with tannic acid: non-thermal effect on the crosslinking process

The reaction of gelatin with tannic acid using microwave heating with simultaneous cooling (MHSC) in comparison with water bath heating was investigated to get some hints on the non-thermal effect of microwave. MHSC showed a better ability to accelerate the reaction rate. It also increased the turbidity, crosslinking degree, and viscosity of the crosslinked gelatin by 91 FTU, 6.8%, and 0.08 respectively, indicating that microwave could improve the properties of the product. Moreover, sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns reflected that the crosslinked gelatin (MHSC) had a higher molecular weight as the gray levels decreased by 9.2% (235–245?kDa), 2.3% (135–145?kDa), and 9.3% (122–132?kDa). More homogeneous aggregations were identified at the crosslinked gelatin by atomic force microscopy. These results proved that microwave has a non-thermal effect in the gelatin crosslinking process, accelerating the crosslinking reaction, and improving the performance of the gelatin product, which may have a good use in industry.     

封闭异氰酸酯与低毒脲醛树脂固化反应特性的探究

对不同固化体系下低毒脲醛树脂以及其与封闭异氰酸酯反应的固化速度、适用期及pH值变化情况进行了研究.结果表明,单组分固化体系中,硫酸铝固化速度最快.磷酸与氯化铵组成的双组分固化体系,固化速度虽然很快,但适用期较短;鸟洛托品对延长脲醛树脂胶的适用期效果较好.加入封闭异氰酸酯后会加快脲醛树脂固化速度,但其适用期有所缩短,而在硫酸铝和磷酸的固化体系中不明显.pH值在15min内下降较快,30min之后趋于稳定.     

Properties of polythiourethanes prepared by thiol–isocyanate click reaction

Polythiourethane networks with systematic compositional variations of thiol [ethoxylated trimethylol‐propane tri(3‐mercapto‐propionate), ETTMP1300 and pentaerythritol tetra(3‐mercapto‐propionate), PETMP] and isophorone diisocyanate (IPDI), i.e., IPDI/ETTMP1300/PETMP = 100/100/0, 100/80/20, 100/60/40, 100/40/60, 100/20/80, and 100/0/100, were prepared by base catalyzed thiol–isocyanate click type reaction where the base catalyst (tributylamine, TBA) was photolytically generated using photolatent amine (TBA·tetraphenylborate salt, TBA·HBPh₄). The kinetics of the polythiourethane network formation investigated using real‐time infrared indicates that the thiol–isocyanate coupling reaction was successfully triggered photolytically and the conversion of both thiol and isocyanate reached near 100% in a matter of minutes. The T_g of the polythiourethane networks progressively increases (–8 to 143 °C by DMTA) as a function of the PETMP content due to the higher extent of crosslinks, also resulting in enhanced rubbery modulus. Very narrow full width at half maximum (15–28 °C) of tan δ peak was obtained for all six sets of polythiourethane networks, which is induced by the highly uniform and dense structures of thiol‐based polymeric network. Energy damping performance of polythiourethane networks measured by nondestructive impact testing exhibited remarkably high (～95%) and the relationship with temperature was in accordance with tan δ peak. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46070.     

Quantitative proton NMR determination of linoleic acid mono-and diesters of polyethyleneglycols via reaction with trichloroacetyl isocyanate

A method has been developed for qualitative identification and quantitative determination of linoleic acid mono- and diesters of polyethyleneglycols with various molecular masses. The method is based on proton nuclear magnetic resonance (NMR) spectroscopy analysis of the product obtained after in situ reaction of the ester mixture with trichloroacetyl isocyanate.     

Easy synthesis of highly fluorescent carbon quantum dots from gelatin and their luminescent properties and applications

A simple approach for the synthesis of fluorescent carbon dots (CQDs) has been developed by the hydrothermal treatment of gelatin in the presence only pure water. The as-synthesized CQDs were found to emit blue photoluminescence (PL) with a maximum quantum yield of 31.6%. Meanwhile, the CQDs exhibit excitation-dependent, pH-sensitive and up-converted PL properties. Importantly, these CQDs are demonstrated to be excellent bioimaging agents and fluorescent ink due to their stable emission, well dispersibility, low toxicity, long emission life time, and good compatibility with cells and macromolecules.     

Transition-metal complex formation with phenyl isocyanate

Complex formation between phenyl isocyanate and cobalt or manganese naphthenate in benzene was determined by the mole ratio method. Complex of 3:1 for cobalt and 2:1 for manganese were found. The method of analysis in this study utilized the characteristic transition-metal visible absorption spectra. Effects of time and metal-salt solution stability are noted.     

Reactions of hydroxyalkyl esters with phenyl isocyanate

In a reaction between 2‐hydroxyethyl methacrylate and phenyl isocyanate (PI), we did not obtain the expected urethane ester monomer but products of its subsequent conversion, namely, ethylene dimethacrylate and ethylene bis(phenylcarbamate). The effects of the structures of various hydroxyalkyl esters on the transformation of the products of their reaction with PI into their respective diesters and alkanediyl bis(phenylcarbamates) were observed with standard spectral methods (IR, ¹H‐NMR) and chromatographic and classical separation techniques. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1357–1367, 2005     

Comparative reactivities of hydroxylated polybutadienes with isocyanate in nitrobenzene

Summary The rates of reactions between two hydroxylated polybutadienes (R-45M and H-110) and 1,6-hexamethylene diisocyanate (HDI) have been studied in nitrobenzene solution in the temperature range from 30 to 60°C. An analytical method was used to follow the kinetics of the reactions. The second-order rate constants were calculated and it was concluded that the reactivities of the two-NCO groups in HDI are identical. The rate of the R-45M/HDI reaction is slightly higher and its activation energy is lower than that of the H-110/HDI reaction. The R-45M/HDI reaction is slower in nitrobenzene solution than in chlorobenzene solution.     

相转移催化亚硫酸氢钠封闭异氰酸酯

使用相转移催化剂四丁基溴化铵催化亚硫酸氢钠固体粉末与溶液中的异氰酸酯PAPI的封闭反应,提高封闭反应程度,并且对该封闭反应的条件（反应温度、催化剂用量、原料配比、反应时间）进行了探索,得到较为满意的结果。     

Polymers with pendant isocyanate groups. I. Dual synthesis and properties of poly(styrene-co-styryl isocyanate)

The copolymer poly(styrene-co-styryl isocyanate) was synthesized directly by radical initiation from two different monomer pairs: styrene–cinnamoyl azide and styrene–styryl isocyanate. The copolymerization parameters r₁ = 0.93 ± 0.08, r₂ = ?0.7 ± 0.8 for the first monomer pair and r₁ = 7.8 ± 0.6, r₂ = 0 ± 0.3 for the second pair were determined according to the conventional scheme of copolymerization. The intrinsic viscosities and the thermal behavior of the various copolymers were determined. Further, the chemical reactivity of the pendant isocyanate groups toward alcohol and amines was investigated.     

Polymers with pendant isocyanate groups. II. Dual synthesis and properties of poly(acrylonitrile-co-styryl isocyanate)

The copolymer poly(acrylonitrile-co-styryl isocyanate) was prepared directly in bulk by radical initiation either from the monomer pair acrylonitrile–cinnamoyl azide or from the pair acrylonitrile–styryl isocyanate. The copolymerization parameters, calculated by the conventional scheme, are r₁, = 3.5 ± 0.5; r₂ = 0 ± 0.5, for the first pair and r₁ = 9 ± 0.5; r₂ = 0 ± 0.5 for the second pair. The basic physical properties (solubility, intrinsic viscosity, and thermal behavior) of the new copolymer were determined and the chemical reactions of the isocyanate group with alcohol and with dimethylformamide were investigated.     

超声波催化亚硫酸氢钠封闭异氰酸酯

使用超声波催化亚硫酸氢钠固体粉末与异氰酸酯(TDI)封闭反应,提高了封闭反应程度,并对该封闭反应的条件(溶剂选择、反应温度、原料配比等)进行了探索。发现在相转移催化亚硫酸氢钠封闭异氰酸酯体系中,超声能够取代相转移催化剂,使反应顺利进行。     

Effects of reaction conditions on intercalation between gelatin and montmorillonite: Thermodynamical impact

To investigate the effects of reaction conditions on a intercalation between gelatin and montmorillonite (MMT) and thermodynamical impact of the intercalation, a series of gelatin/MMT hybrids were prepared by changing the reaction conditions (weight ratio of gelatin and MMT, pH, concentration of gelatin solution and MMT suspension, and reaction temperature).The hybrids were characterized by X‐ray diffraction, transmission electron microscopy, atomic absorption spectroscopy, and thermogravimetric analysis. The results showed the intercalation between gelatin and MMT, which was a faster process than the melt intercalation of some synthetic macromolecules such as polystyrene, achieved a thermodynamically stable state in 5 min. All the other reaction conditions, except reaction temperature, affected the intercalation between gelatin and MMT. The reaction was driven by enthalpy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Physical properties of wool fibers modified with isocyanate compounds

Wool fibers were chemically modified with various kinds of isocyanates and diisocyanates. The reactivity of these modifying agents was examined as a function of the reaction solvent, temperature, time, and isocyanate chemistry. The use of dimethyl sulfoxide as the solvent, aliphatic mono and bifunctional isocyanates, such as dodecyl isocyanates and hexamethylene diisocyanate, and a temperature of 75°C resulted in higher weight gains. The moisture content of wool fibers tended to decrease with increasing the weight gain, the extent of which depended on the isocyanate used. Monofunctional isocyanates caused a sharp drop of tensile strength and an increase of elongation at break, while bifunctional isocyanates preserved the intrinsic tensile properties of wool. The FTIR spectra showed changes in the amide I, II, and III ranges, in the CO stretching range at 1750–1700 cm^?1, and in the CH stretching and bending regions at 3000–2800 and 1500–1350 cm^?1, respectively, attributable to the incorporation of the modifying agent. DSC measurements highlighted remarkable changes in the thermal behavior of acylated wool fibers. The bimodal melting endotherm at 230–240°C shifted to lower temperature, and the relative intensity of the constituent peaks changed as a function of the weight gain. Foreign deposits adhering to the surface of chemically modified wool fibers were detected by SEM analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1390–1396, 2003     

Ductile PLA modified with methacryloyloxyalkyl isocyanate improves mechanical properties

The majority of the biodegradable polymers in clinical use are composed of stiff materials that exhibit limited extendibility with unsuitably high Young’s modulus and low elongation at break values that make them non-optimal for various biomedical applications. Polylactide (PLA) is often used as a biomedical material because it is biodegradable, but the physical and mechanical properties of PLA need to be improved for biomedical applications. In order to improve the flexibility and strength of biodegradable PLA, various reaction conditions were studied. Urethane structure polymer materials were prepared; PLA was reacted with a small amount of methacryloyloxyethyl isocyanate (MOI) to obtain a ductile PLA with markedly improved mechanical properties. Elongation at break increased by 20 times when compared to neat PLA. Impact resistance (notched) improved 1.6 times. Thus, this modified PLA biodegradable polymer may have greater application as a biomedical material with increased mechanical properties.     

Toughening epoxy resin with blocked isocyanate containing soft chain

A series of imidazole (MI) blocked 2,4‐toluene diisocyanate (TDI) with polyethylene glycol (PEG‐400) as soft segment (PEG‐MI‐b‐TDI) were synthesized for toughening and curing the bisphenol A type epoxy resin (E‐44). Fourier transform infrared (FTIR) spectrum indicates that the NCO groups of the isocyanate molecule are blocked with MI. For curing epoxy systems, elimination of epoxy group and the formation of urethane bonds were studied by FTIR spectroscopy. The results of mechanical property were shown that the tensile shear and impact strengths of neat MI and MI‐b‐TDI cured E‐44 are lower than those of PEG‐MI‐b‐TDI cured E‐44. Based on the scanning electron microscope studies, microstructure evolutions of the E‐44 cured by different curing agents were imaged. The mechanical, thermal, and dynamic mechanical properties were measured by universal testing machine, differential scanning calorimeter and dynamic mechanical analyzer (DMA). The toughness of E‐44 cured by PEG‐MI‐b‐TDI was effectively improved without sacrificing the tensile shear strength. Based on the DMA studies, the long soft chain of PEG brought in a noticeable lowering in the glass transition temperature (T_g). The glass transition temperature is near 165°C for the neat MI cured E‐44, which is higher than the T_gs of the other curing agents cured epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41345.