Presence Of Dibutyltin Dilaurate Research Articles

Revealing Dynamic Behavior in High Dielectric Poly(thiourethane)-Based Vitrimer-like Materials.

Here, we have explored covalent adaptable networks (CANs) comprising poly(thiourethane)-based systems (PTUs). The PTUs were synthesized through the combination of thiol and isocyanate monomers in stoichiometric proportions, in the presence of dibutyltin dilaurate (DBTDL) as catalyst. Dynamic mechanical analysis (DMA) provided detailed insight into the vitrimeric behavior. Through these investigations, we evaluated the viscoelastic, thermomechanical, and vitrimeric properties. Additionally, broadband dielectric spectroscopy (BDS) revealed the various relaxation processes inherent in such vitrimer-like materials. We methodically examined the evolution of each relaxation in every prepared sample to comprehend the operational mechanisms in these vitrimer-like systems. Our findings underscore that depending on the PTU formulation, the glass transition temperature (Tg) and the topology freezing transition temperature (Tv) can be effectively distinguished and studied. Considering the high dipole moment of the dynamic bonds present in these systems, there is potential for utilizing them as dielectric materials working under the concept of dipolar glass polymers. Furthermore, the reversibility exhibited by their inner chemical structures positions them as promising candidates for active layers in capacitor devices, particularly for energy-related applications, with the ability to be recyclable while maintaining almost invariant both their mechanical and dielectric properties, thus promoting the extension of the lifespan of electronic devices.

Morphological, Thermal, Physicomechanical and Optical Properties of Crosslinked Poly (Ester-Urethane-Acrylate): Effect of Added Methyl Methacrylate

Poly (ester-urethane-acrylate) (PEUA) macromonomer was prepared by reacting two moles of isophorone diisocyanate (IPDI) with one mole of bis (1,4-butanediol ortho-phthalate) (BPE), followed by end-capping with two moles of 2-hydroxyethyl methacrylate (HEMA) in the presence of dibutyltin dilaurate (DBTDL) catalyst. Thereafter, different ratios of methyl-methacrylate (MMA) were added to the PEUA macromonomer to prepare crosslinked PEUA/MMA sheets. Fourier transform infrared spectrometry (FTIR), ultraviolet-visible spectrophotometry (UV-vis) and differential scanning calorimetry (DSC) techniques were employed to investigate the structure, optical transparency and thermal properties of the crosslinked sheets. The effect of MMA on the polymerization shrinkage and abrasive wear properties of PEUA and their copolymers were also studied. The polymerization shrinkage study showed that PEUA copolymer containing 40 wt% MMA had a more rigid microstructure with improved volume shrinkage and abrasive wear properties as compared with the other compositions of PEUA copolymers with MMA loadings of 80, 60 and 20%. The improvement was attributed to the better miscibility and compatibility of 40 wt% MMA with the PEUA as revealed by DSC, heat deflection temperature (HDT) and scanning electron microscope (SEM) studies.

Thermoresponsive hollow polymeric shell nano/microparticles with interconnected nanoholes

AbstractPNIPAAm‐grafted thermoresponsive hollow nano‐holed polymeric‐shell (HHPS) particles were fabricated from surface‐modified colloidal silica (CS) with poly(ethylene glycol) methyl ether‐3‐(triethoxysilyl)propyl isocyanate (PEGME‐IPTES) and 3‐(trimethoxysilyl) propyl methacrylate (MPS) as templates. The polymeric shells were then synthesized through a “grafting‐through” approach via surface‐initiated polymerization of N‐isopropyl acrylamide (PNIPAAm) using potassium persulfate (KPS) as an initiator, followed by the etching of CS with hydrofluoric acid to remove the CS core templates. CS nanoparticles and PEGME‐IPTES were presynthesized using tetraethoxysilane (TEOS) and distilled water in methanol with ammonia solution as a catalyst by the sol–gel method and using 3‐(triethoxysilyl) propyl isocyanate (IPTES) with poly(ethylene glycol) methyl ether (PEGME) in the presence of dibutyltin dilaurate. The chemical structures of bare and modified CS, PNIPAAm, PNIPAAm‐CS, and HHPS particles were characterized by FT‐IR and NMR spectroscopies. SEM and TEM images confirmed that the resulting HHPS particles had a significant number of interconnected nanoholes. To evaluate the LCST behaviors of HHPS particles, the transition of transmittance and the changes in particle diameter according to the temperature change were measured through UV‐vis spectroscopy, DLS, and microscopy.

Controlling the reactivity of hydrophilic bark extractives as biopolyols in urethane-formation reactions using various catalysts

The composition, functionality, and reactivity of black alder (Alnus glutinosa) bark extractives as a biopolyol with polymeric diphenyl methane diisocyanate (PMDI) have been studied using a variety of methods, including HPLC, GPC, GC, wet chemistry, and isothermal calorimetry. The Black alder (BA) bark extractives were identified as a prospective polyol consisting mainly of the oregonin-xyloside form of diarylheptanoid, which contains OH groups that are almost equally represented by phenolic and aliphatic origins. To identify catalysts that effectively increase the reactivity of low-active phenolic OH groups in urethane formation reactions, the kinetics of extractives and model compounds' interaction with PMDI catalyzed with tin organic, dibutyl tin dilaurate (DBTDL) and tertiary amine, 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst in dimethylsulfoxide (DMSO) solution were studied. The results showed that DABCO resulted in a fourfold higher reactivity of phenolic groups with PMDI compared to DBTDL catalyzed reactions. Furthermore, the reactivity of phenolic groups with PMDI catalyzed by DABCO was almost twofold greater than that of aliphatic OH catalyzed by DBTDL. The second-order constants of 31.9 × 10−4 mol·L−1·s−1 and 53.7 × 10−4 mol·L−1·s−1 were determined for the interaction of extractives with PMDI in the presence of DBTDL and DABCO, respectively. The disappearance of the radical scavenging effect of phenolic compounds in extractives derived PU elastomers obtained with DABCO catalyst indicates complete reactions of phenolic groups with isocyanate, while these groups remain partly free in the case of DBTDL catalysis. It is assumed that a combination of DBTDL and DABCO catalysts will be necessary to achieve high crosslinking while leaving a small portion of free phenolic groups in the bio-based PU network, thus obtaining material with high mechanical properties and thermal oxidative stability.

Trisurethane functionalized sulfonamide based polymeric sorbent: Synthesis, surface properties and efficient mercury sorption from wastewater

In this study, trisurethane modified sulfonamide based polymeric adsorbent was prepared starting from reaction with chlorosulfonated poly (styrene) (PS) beads and tris(hidroxymethyl) aminometane. Hydroxyl functions of the adsorbent were reacted with butyl isocyanate in the presence of dibutyltin dilaurate as a catalyst at 60 0C for 48 h to obtain tris urethane functional polymeric adsorbent (PS-TUR). Spectroscopic and morphological characterizations of the polymeric adsorbents were carried out using scanning electron microscopy (SEM-EDX), infrared spectrophotometry (FTIR), XPS and analytical methods.The surface properties of PS-TUR were investigated for the first time with the inverse gas chromatography technique at infinite dilution before adsorption studies. The dispersive surface energy of adsorbent was determined according to the method of Schultz (55.54–61.73 mJ m−2) and Dorris-Gray (57.70–67.03 mJ m−2). Adsorption enthalpy and Gibbs free energy were calculated according to this technique and it was determined that the adsorption was exothermic and spontaneous. As a result of the analyzes made with this technique, it was determined that the PS-TUR adsorbent surface was acidic (KD/KA=0.27<1) and optimum conditions (pH: 7, dose: 0.10 g) were determined for the effective adsorption of Hg (II) ions. Surface acidity-basicity behavior of sorbent was determined by isoelectric point (IEP: 6.20) and pHpzc (5.81) analyses.Batch adsorption studies of the PS-TUR adsorbent were carried out as a function of adsorbent dosage, pH, initial metal ion concentration (0.0025–0.1000 mol/L), and kinetically. After determination of optimum adsorbent dosage was found as 100 mg, mercury sorption capacity of PS-TUR adsorbent was found as 511.50 mg g−1 adsorbent.Desorption studies were carried out using glacial acetic acid and studies demonstrated that PS-TUR adsorbent is regenerable and can be successfully used for four adsorption–desorption cycles without significant loss its capacity.Also, PS-TUR adsorbent shows selectivity with high sorption capacity towards mercury as compared to other metal ions.

Thermal degradation and hemocompatibility of polyurethane cellulose nanocomposites

Bio based polymers are reinforced with natural fibers as a good candidate to the replacement of synthetic materials. In this work biobased polyurethane cellulose nanocomposites (PUCNs) prepared from hydroxylated olive oil and diphenyl methane - 4, 4 - diisocyanate,in the presence of dibutyl tin dilaurate as catalyst and incorporated with varying concentration of cellulose nanocrystals. The polyurethane cellulose nanocomposites films have been characterized by FTIR, XRD, SEM and TGA/DTA studies. The compatibility of the nanocomposites is evaluated by invitro hemolytic assay method. The FTIR analysis indicates the presence of the cellulose nanocrystals in the polyurethane matrix. The formation of urethane linkage is confirmed by the stretching vibrations of the peak around 3330 cm-1. XRD diffraction pattern of the samples shows a increase of 2% crystallinity by the addition of cellulose nanoparticles. The average size of cellulose nanocrystals is calculated as 16nm. SEM images shows a rod like structure of cellulose nanocrystals and the fine dispersion of cellulose nanocrystals in the polymer matrix. The degradation of PUCNs is more pronounced in different chemical environments than polyurethane. Thermogravimetric analysis observed that the addition of cellulose nanocrystals increases the thermal stability of PUCNs upto 300oC.

Synthesis and performance of bio-based hyperbranched polyol in polyurethane coatings

In the present work, the bio-based hyperbranched polyol (COHBP) was prepared by using castor oil and dimethylol propionic acid (DMPA). The molecular structure of COHBP was determined by FTIR and NMR. Polyurethanes of castor oil (PU−COs) and castor oil based hyperbranched polyol (PU−COHBPs) were prepared by using various diisocyanate as cross-linking agent at NCO: OH, ratio of 1.2:1, in presence of dibutyltin dilaurate (DBTDL) as catalyst. Finally, these polyurethanes were coated on glass plate and mild steel panels. Thermal behavior of PU−COs and PU−COHBPs were studied by thermo-gravimetric analyzer (TGA). The mechanical properties of the coated panels were estimated by performing various tests such as cross-cut adhesion, scratch resistance, impact resistance, mar resistance, flexibility, and pencil hardness. Chemical resistance property of coating was evaluated by immersion method. The polyurethanes films were characterized by gel content. The corrosion rate of each coating plate was determined by electrochemical method. The surface morphology of coating films was studied by AFM and SEM, while their crystallinity was estimated by XRD analysis. The properties of PU−COHBPs were compared with PU−COs. It was found that PU−COHBPs showed excellent coating performance as compared to PU−COs.

Recyclable poly(thiourethane) vitrimers with high Tg. Influence of the isocyanate structure

Abstracts Networked poly(thiourethane) materials with Tgs around 130 °C, derived from two aliphatic isocyanates (isophorone diisocyanate, IPDI and 4,4′-methylene bis(cyclohexyl isocyanate), HMDI) and one aromatic diisocyanate (toluene-2,4-diisocyanate, TDI) have been prepared with the same trithiol as comonomer (trimethylol propane tris(3-mercaptopropionate), S3) in stoichiometric proportions in the presence of dibutyltin dilaurate (DBTDL) as the catalyst. The higher reactivity of TDI allowed the preparation of this material in absence of catalyst. The evolution of the curing process has been followed by FTIR. Thermomechanical studies have been performed to determine their viscoelastic properties and their vitrimeric behaviour. The materials were able to reach a complete relaxation stress state thanks to the exchange process of the thiourethane moiety. Among them, TDI derived material experimented the fastest relaxation. The materials were also characterized by thermogravimetry and tensile tests. The recycled materials obtained by grinding the original thermosets and hot-pressing the powder have been fully characterized by mechanical, thermomechanical and FTIR studies, which allowed to confirm their recyclability without appreciable changes in the network structure. The presence of DBTDL in the materials has been proved to be necessary to reach a good recyclability.

A new class of vitrimers based on aliphatic poly(thiourethane) networks with shape memory and permanent shape reconfiguration

Vitrimers are a new promising class of polymeric materials which are attracting increasing attention thanks to their thermosetting characteristics with their capability of being reprocessed and recyclable, which make them more environmentally friendly in reference to the conventional thermosets. In the present study, we report a new class of vitrimeric materials consisting in poly(thiourethane) networks. These materials can be easily prepared from readily available isocyanate and thiol monomers in the presence of dibutyltin dilaurate (DBTDL) as the catalyst. The reaction has a click nature and therefore leads to highly homogeneous networks. The materials studied behave as conventional thermosets until topological rearrangement started. Freezing topological temperatures (Tv) between 132 and 95 °C were determined depending on the amount of catalyst in the material. The vitrimers prepared showed good shape memory and welding abilities and a high optical transparency and therefore they have a great potentiality in advanced engineering applications. The occurrence of the trans-thiocarbamoylation reaction, responsible of the rearrangement, has been confirmed by using model compounds. The materials remained unaltered after reprocessing, which was proved by means of FTIR and thermomechanical studies.

Reactive blending and transesterification-induced degradation of isosorbide-based polycarbonate blends

We report the reaction of bio-renewable isosorbide-based polycarbonate (IcC-PC) with poly(bisphenol A carbonate) (BPA-PC) by melt-blending in the presence of dibutyltin dilaurate (DBTDL). The blends formed copolymers and transformed into transparent alloys with a single Tg after melt-blending. A remarkable reduction in molecular weight was observed in the reactively blended products. 1H NMR and 13C NMR results showed that the carbonate group of IcC-PC is less vulnerable to nucleophilic attack than that of BPA-PC and that transesterification is initiated by the exchange reaction between the laurate ligands of DBTDL and the carbonate groups of BPA-PC. Tin-containing BPA-PC chains were proposed to react with the carbonate group of IcC-PC via a coordination-insertion mechanism to produce the (IcC-PC)-(BPA-PC) copolymer. The hydroxyl end-groups of IcC-PC were also involved in transesterification under the catalysis of dibutyltin compounds and converted into low-reactive phenolic end-groups of BPA-PC. Degradation in the IcC-PC/BPA-PC blends after adding DBTDL was mainly caused by the exchange reaction between DBTDL and BPA-PC, hydrolysis, and phenolysis of IcC-PC and BPA-PC under the catalysis of dibutyltin compounds. Among these reactions, hydrolysis played the major role and occurred mostly at the BPA-PC chains.

Synthesis and characterization of transparent high-refractive index polyurethanes

ABSTRACTIn this study, high-refractive index carbazole-based polyurethanes (CBPs) were prepared. Firstly, bifunctional carbazole derivatives (BCDs) were synthesized by reacting 9-(2-oxiranylmethyl)-9H-carbazole with bisphenol A. Then, CBPs were prepared by step-growth polymerization of BCDs and isophorone diisocyanate in the presence of dibutyltin dilaurate. The polymer solution was spin-coated on a silicon wafer or a glass plate, and the sample was dried under nitrogen to give a transparent film. The product was characterized by 1H-NMR, GPC, TGA and DSC. The refractive index of the film was measured by spectroscopic ellipsometry. The transmittance of polyurethane films was observed by a UV-visible spectrometer. The refractive index of CBPs was 1.62 on average at 400 to 750 nm. The results suggest that the polyurethane films are promising materials for application in display industry.

UV-curable urethane acrylate zirconium oxide nanocomposites: Synthesis, study on viscoelastic properties and thermal behavior

In the present study, UV-curable urethane acrylate was synthesized by the reaction of isophorone diisocyanate with1,4-butanediol and 2-hydroxyethyl methacrylate in the presence of dibutyltin dilaurate as a catalyst and acetone as a solvent. The structure of urethane acrylate oligomer was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. In order to examine the influence of inorganic phase of zirconium oxide nanoparticles on characteristics of synthesized resin, organic–inorganic nanocomposites were prepared by urethane acrylate resin and nano zirconium oxide with 1, 3, and 5 wt%. In order to improve nanoparticles dispersion, the surface of zirconium oxide nanoparticles was modified by vinyltrimethoxysilane coupling agent. The analysis of nanoparticle surface modification by Fourier transform infrared spectroscopy and scanning electron microscopy suggested a good reaction of vinyltrimethoxysilane with the surface of zirconium oxide nanoparticles. The characteristics of the prepared nanocomposites were evaluated through thermogravimetric analysis and dynamic mechanical thermal analysis. All of conducted tests represented improved thermal stability properties, storage modulus, and viscoelastic properties of urethane acrylate–zirconium oxide nanocomposites in comparison with polymeric coatings without nanoparticles.

High-refractive-index polymers of poly (carbazole phenoxy-based polyurethane) for a refractive index matching film in organic light-emitting diodes

ABSTRACTA high-refractive index polymer of carbazole phenoxy-based polyurethane (CPP) was prepared by step-growth polymerization. Initially, bicarbazole phenoxy (BCP) derivatives were synthesized by the reaction between 9-(2-oxiranylmethyl)-9H-carbazole and 4,4′-(1-phenylethylidene)bisphenol. The step-growth polymerization of BCP and isophorone diisocyanate took place at 80°C in the presence of dibutyltin dilaurate as a catalyst affording the prepolymer with isocyanate end-groups. The CPP was obtained by the chain extension reaction of the prepolymer and bis-(2-hydroxyethyl) disulfide as an extender agent. The polymer was characterized by 1H NMR, FT-IR, and GPC. The CPP solution was spin-coated on a silicon wafer and dried under nitrogen. The transmittance of the CPP film was almost 100% as analyzed by a UV-visible spectrometer and the refractive index of the polymer was 1.63 as measured by spectroscopic ellipsometry. The result indicated that the high-refractive index CPP could be a promising material for optoelectronic device applications.

Effect of branching in hyperbranched alkyd on the performance of alkyd polyurethane coating

ABSTRACTHyperbranched alkyd was synthesized by single‐step approach using trimethylolpropane, mono pentaerythritol as core material, and 2,2‐bis(methylol)propionic acid (DMPA), a combination of dehydrated castor oil fatty acid and coconut oil fatty acid as chain extender. A series of hyperbranched alkyds were prepared at different degree of branching in the alkyd structures by changing the amount of DMPA in the alkyd resin formulation. The resins were characterized by Fourier transform infrared and 1H‐nuclear magnetic resonance (NMR) spectroscopic technique. These hyperbranched alkyds were converted into polyurethane coating after reaction with hexamethylene diisocyanate trimer at a definite ratio in the presence of dibutyltin dilaurate as a catalyst. The effect of branching and polymeric chain entanglement on the glass transition temperature, Tg of the alkyd polyurethane coating (APUC) was studied by differential scanning calorimetry technique. The performance of such APUC in terms of gloss, gloss retention under accelerated QUV radiation, natural outdoor exposed condition, mechanical, and corrosion resistance properties were enhanced with the increase of polymeric chain entanglement, i.e., compactness or higher order of branching in the alkyd resin structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45835.

Synthesis and characterization of crosslinked transparent poly(ester-urethane-acrylate) containing methyl methacrylate

The current study deals with the synthesis of various compositions of crosslinked poly(ester-urethane-acrylate) (PEUA)/methylmethacrylate (MMA) copolymer employing free radical polymerization. Initially, (1,4-butanediol) orthophthalate (BPE) polyester polyol has been synthesized by reacting 1,4 butanediol (BDO) and phthalic anhydride (PA). Subsequently the PEUA prepolymer was formed by reacting one mole of BPE with two mole of isophorone diisocyanate (IPDI) followed by end capping with two mole of 2-hydroxyethyl methacrylate (HEMA) in the presence of dibutyltin dilaurate (DBTL) catalyst. Finally, different compositions of crosslinked PEUA/MMA copolymer were prepared by reacting the PEUA prepolymer with MMA, in the presence of 1% azobisisobutyronitrile (AIBN) (w/w) as a chain initiator. The formation of BPE, PEUA and copolymers was confirmed by Fourier transform infrared (FT-IR) and 1H NMR spectroscopy. Water uptake, mechanical, thermal and optical properties of PEUA, PMMA and their copolymers have been also investigated. The impact fractured surface morphology of copolymers was observed using scanning electron microscope (SEM). The results showed that the increased miscibility, improved mechanical and physical properties of copolymer was influenced by the crosslink density. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), Haze and transparency of PEUA/MMAcopolymers were determined. The copolymer with 40 wt% MMA loading exhibited optimum mechanical and physical properties with respect to the other compositions.

Effect of polyester polyol chain length on the properties of transparent poly (ester-urethane-acrylate)/MMA copolymer for optical applications

A series of poly(ester-urethane acrylate)/methyl methacrylate (PEUMA) crosslinked copolymers were prepared using hydroxyl terminated aromatic polyesters (PEs) with varying chain lengths. Four kinds of PEs with terminal hydroxyl groups were synthesized by reacting phthalic anhydride (PA) with 1,2- propanediol (PDO), 1,4-butanediol (BDO), 1,6-hexanediol (HDO) and diethylene glycol (DEG) respectively. The resultant PEs were reacted with isophorone diisocyanate (IPDI) in the presence of dibutyltin dilaurate (DBTDL) catalyst and end capped with 2-hydroxyethyl methacrylate (HEMA) to obtain ester-urethane-acrylate (EUA) prepolymer. Thereafter, crosslinked PEUMA copolymer were synthesized by reacting the EUA prepolymer with 40% (w/w) methyl methacrylate (MMA) in the presence of 1% azobisisobutyronitrile (AIBN) chain initiator. The PEs and EUA prepolymer were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, and gel permeation chromatography (GPC) techniques. The average molecular weights (Mc) between two crosslinks of the samples were determined by using the Flory Rehner equation. The tensile modulus, flexural strength, thermal properties and transparency of PEUMA copolymers were also determined and correlated with the average molecular weight and crosslinked density. The transparency of PEUMAs was found to be above 90% and hence it is an excellent alternative to glass for optical applications.

Synthesis and characterization of vegetable oil based polyurethane derived from low viscous bio aliphatic isocyanate: Adhesion strength to wood-wood substrate bonding

In the current study, biobased polyurethane (PU) adhesives at three different stoichiometric ratios of hard (NCO) to soft segment (OH) (1.1:1, 1.3:1, 1.5:1) were prepared by reacting castor oil (CO) based polyol with partially biobased polyisocyanate (PBPI) in the presence of dibutyltin dilaurate (DBTDL) as catalyst. The synthesis of PU adhesive films such as CO-PU1.1:1, CO-PU1.3:1, and CO-PU1.5:1 was confirmed by Fourier transform infrared (FTIR) spectroscopy. The effect of stoichiometric ratios on the bonding strength of wood-to-wood substrate was studied using lap shear strength test. The change in lap shear strength of PU adhesive films subjected to acid and alkali solution was tested. The chemical resistance, surface properties and wetting energies of PU adhesive films were evaluated using scanning electron microscopy (SEM) analysis and contact angle measurement. Thermal stability and activation energy of the films were determined employing thermogravimetric analysis (TGA). The experimental result showed that CO-PU1.3:1 exhibited higher adhesive strength, where as CO-PU1.5:1 exhibited higher thermal stability.

Clickable polyurethanes based on s‐triazine ring containing aromatic diisocyanate bearing pendent alkyne group: Synthesis and postmodification

ABSTRACTA new s‐triazine ring containing aromatic diisocyanate bearing a pendent alkyne group, namely, 2,4‐bis(4‐isocyanatophenoxy)−6‐(prop‐2‐yn‐1‐yloxy)−1,3,5‐triazine was synthesized and reacted with various diols viz., 1,10‐decanediol, tetraethylene glycol and polyethylene glycols in the presence of dibutyltin dilaurate as the catalyst to obtain a series of linear polyurethanes. The selected polyurethanes possessing pendent alkyne groups were postmodified with chemically diverse azides viz., 1‐(azidomethyl)benzene, 1‐(azidomethyl)pyrene, and methoxy end‐caped poly(ethylene glycol) azide via copper‐catalysed azide‐alkyne Huisgen 1,3‐dipolar cycloaddition. FTIR and 1H NMR spectra indicated quantitative click reaction. UV–vis and fluorescence spectroscopic analysis confirmed complete incorporation of pyrenyl groups indicating the formation of fluorescence active polyurethane by postmodification with 1‐(azidomethyl)pyrene. TG analysis of polyurethanes indicated two stage weight loss and their thermal stability, as judged by T10 values, was governed by weight percent of urethane linkages. The water contact angle measurements revealed improved wettability with increased content of PEG either in the backbone of polyurethanes or as grafted chains. DLS and TEM studies confirmed that certain polyurethanes possessing PEG segments displayed self‐assembly in aqueous solution, which was further supported by pyrene encapsulation studies using UV–vis spectroscopy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1008–1020

Folic acid and trastuzumab conjugated redox responsive random multiblock copolymeric nanocarriers for breast cancer therapy: In-vitro and in-vivo studies

The study represents synthesis, characterization and biological evaluation of redox responsive polymeric nanoparticles based on random multiblock copolymer for doxorubicin delivery in breast cancer. The random multiblock copolymer was synthesized via ring opening polymerization of lactide with polyethylene glycol to form triblock copolymer followed by isomerization polymerization of the triblock copolymer and 2-hydroxyethyl disulfide with the help of hexamethylene diisocynate in presence of dibutyltin dilaurate as a catalyst. Folic acid was conjugated to hydroxyl group from the multiblock polymer through DCC-NHS coupling. High drug loading content of ∼22% was achieved in the polymeric nanoparticles with size range of ∼110nm and polyethylene glycol fraction of ∼18% in the multiblock copolymer. Drug release profile confirmed the redox responsive behavior of polymeric nanoparticles with ∼72% drug release at pH 5.5 in presence of 10mM GSH as compared to ∼18% drug release at pH 7.4. In vitro cellular uptake studies showed ∼22% cellular uptake with dual (folic acid and trastuzumab) conjugated polymeric nanoparticles as compared to non-targeted polymeric nanoparticles. Fluorescence activated cell sorting (FACS) studies demonstrated higher apoptosis (∼80%) as compared to non-conjugated polymeric nanoparticles (20%) in MCF-7 cell line. In vivo studies showed 91% tumor regression in Ehrlich ascites tumor (EAT) as compared to free doxorubicin treated mice without showing any significant toxicity. Thus, it is envisaged that these redox responsive polymeric nanocarriers act as Trojan horses in cancer therapeutics.

Research on the Blocking Reaction Kinetics and Mechanism of Aqueous Polyurethane Micelles Blocked by 2,4,6-Trichlorophenol

The blocked terminal-isocyanate (NCO) aqueous polyurethane micelles were prepared by using the 2,6-hexamethylene diisocyanate (HDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), and 2,4,6-trichlorophenol (TCP) as blocking agent. This paper was focused on the kinetics research of the TCP blocking terminal-NCO of pre-polymer, which occurred during the preparation process of TCP blocked aqueous polyurethane micelles. The kinetics parameters were obtained in the absence and presence of dibutyl tin dilaurate (DBTDL) as catalyst, respectively. Furthermore, the mechanism for TCP blocking terminal-NCO of pre-polymer was explored. The results showed that the blocking reaction was second order reaction, and the reaction activation energy was 43.890 KJ/mol without catalyst. In the presence of DBTDL, the blocking reaction activation energy was reduced to 34.412 KJ/mol, and the reaction rate was improved significantly. In addition, TCP blocking terminal-NCO of pre-polymer could be ascribed to the nucleophilic addition between nucleophilic phenolic hydroxyl of TCP and the carbon atom of -NCO group.