Di-n-butyltin Dilaurate Research Articles

Development of a Composite Material Based on Polymers Polydimethylsiloxane and Polytetrafluoroethylene Use in Human Prosthetic Coatings

The purpose of this study is the development of a composite material composed of a main layer of polydimethylsiloxane (PDMS) and a reinforcement of polytetrafluoroethylene (PTFE), to be used later in human prosthesis coatings. A mass ratio of the main layer consisting of PDMS:Tetraethyl orthosilicate (TEOS):Di-n-butyl tin dilaurate (DBTL) in the range of 33:1:0.5; 25:1:0.5; 10:1:0.5, and the mass ratio of the composite material (PTFE:PDMS) with a range was evaluated of 1:9; 1:1; 2:3. Obtaining the following results: Tensile strength of 0.085 MPa based on the ratio of 33:1:0.5 - 1:9 and 0.59 MPa with respect to the ratio of 10:1:0.5 - 2:3, evidencing an increase in tensile strength by decreasing the weight of PDMS and increasing the weight of PTFE. On the other hand, the composite material obtained is hydrophobic, insoluble in ethanol and water, has a cross-linking percentage of 98.74 % and 99.66 % respectively, also has a minimum permeance of 5.24x10-7 (g Pa-1 s-1 m-2). With which it is concluded that the treatment whose properties resemble the human skin is the combination 10:1:0.5 - 1:1 that allowed to obtain an average tensile strength of 0.66 MPa, average modulus of elasticity of 6.56 MPa, similar to the dermis of a 43 year old person.

Preparation and Separation Properties of Oleyl Alcohol-Modified PDMS Membranes

Polydimethylsiloxane (PDMS) pervaporation (PV) membranes are promising for the recovery of aromatic compounds in water. The novel oleyl alcohol-modified PDMS membranes were prepared using n-heptane as solvent, tetraethyl orthosilicate (TEOS) as crosslinker, di-n-butyltin dilaurate (DBTL) as catalyst and oleyl alcohol as organic modifier. The PV performances were investigated for separating phenol/water mixtures at different temperatures. The results showed that the oleyl alcohol-modified PDMS membranes had better selectivity than those without oleyl alcohol. For 0.50 wt% phenol in feed mixture at 80 °C, these membranes had a flux of 0.115 kg m-2 h-1 and separation factor of 8.77.

Surface Modification of Polycarbonate Urethane with Zwitterionic Polynorbornene via Thiol‐ene Click‐Reaction to Facilitate Cell Growth and Proliferation

Herein, we grafted the zwitterionic polynorbornene onto polycarbonate urethane (PCU) film surface by a convenient route of thiol‐ene click‐chemistry. The PCU film surface was first treated with hexamethylene‐1,6‐diisocynate and subsequently with two different thiol agents (l‐cysteine and β‐marcaptoethanol) in the presence of di‐n‐butyltin dilaurate (DBTDL) to immobilize sulfhydryl groups onto the surface. Here, DBTDL acted as selective catalyst for the reaction between surface‐tethered isocyanates and amine/hydroxyl groups in thiol agents over that of free thiol groups. In the next step, zwitterionic polynorbornene (poly(NSulfoZI)) having functionalizable double bonds was grafted onto these surfaces by photo‐initiated thiol‐ene click‐reaction. The modified surfaces were characterized by water contact angle and XPS analysis. Moreover, the cytocompatibility of these surfaces was investigated by model endothelial cells, EA.hy926, for 1, 3, and 7 d culture times, which showed enhanced cell adhesion and growth. Therefore, the poly(NSulfoZI) functionalized PCU surface using l‐cysteine as thiol agent could be a good candidate for tissue engineering material application.

Surface modification of polycarbonate urethane by covalent linkage of heparin with a PEG spacer

Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing, αω-diamino-poly(ethylene glycol) (APEG, M n=2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm2) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface.

The effect of adding PDMS-OH and silica nanoparticles on sol–gel properties and effectiveness in stone protection

Inorganic–organic hybrid crack-free xerogels were obtained using di-n-butyltin dilaurate (DBTL) as a catalyst containing tetraethoxyorthosilicate (TEOS) and hydroxyl-terminated polydimethylsiloxane (PDMS-OH) as an additive. We studied the effect of gelling time and sol pH on DBTL concentration. The xerogels’ structure was studied by FTIR, TGA–DTA and SEM techniques. The results showed that the catalyst (DBTL) would substantially shorten the gelling time of the sol. With the addition of PDMS-OH, the viscosity of the sol increased while the gel time decreased. In addition, we noticed an improvement in the cracking of the xerogel with the addition of PDMS-OH. However, the xerogels were opaque when mole ratio of PDMS/TEOS is higher than 0.153. Addition of silica nanoparticles at 0.1% (w/v) in sol could increase xerogels’ surface roughness and hydrophobicity and did not change color of the xerogels. The protective performance evaluated by its ability to resist acid rain revealed that the protective effects were satisfying.

Viscoelastic characterization of TEOS sols in three different solvents when DBTL is used as polycondensation catalyst

The gelation process of TEOS sols in three different solvents using di-n-butyltin dilaurate (DBTL) as polycondensation catalyst has been investigated. Sol compositions were similar to those employed in the field of stone consolidation for the conservation of historical buildings. Three different systems were studied: TEOS in ethanol (S-EtOH) which was tested to explain gelation in protic solvents; TEOS in a mixture of methylethylketone/acetone (S-MA) to represent aprotic solvents; and TEOS in a blend of MEK/ethanol (S-ME) for comparison of a system with properties intermediate between protic and aprotic solvents. The gelation process was studied by measuring the viscoelastic behavior near the gelation point (GP). A scaling exponent (Δ) was determined for the elastic modulus, G(ω)′ and the viscous modulus, G′′(ω), which both follow the same power law, ωΔ, at GP. The fractal dimension, df, was calculated from the scaling exponent, Δ, for each TEOS-DBTL system. For each type of solvent studied, values of Δ from 0.34 to 0.53 with df of 1.9–2.2 were obtained. The results suggest that DBTL leads to a TEOS polycondensation mechanism similar to that observed for a base-catalyst system. However, the change in df suggests that there is a significant effect of the solvent on aggregation mechanisms of the gelation process. A diffusion limited cluster–cluster aggregation mechanism (DLCCA) was observed when ethanol was used as protic solvent, while a reaction limited cluster–cluster aggregation mechanism (RLCCA) was observed for MEK/acetone (aprotic solvent).

Synthesis and Properties of Polyurethanes of Hexamethylene Di-Isocyanate with Multifunctional Chromophores in the Main Chain

Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl) groups in the main chain were synthesized by polyaddition reactions of diols such as bis(4-hydroxyphenylazo)-2,2′-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo-4′-hydroxyphenylazo-2,2′-dinitrodiphenylmethane and bis(4-hydroxy-3-methylphenylazo)-2,2′-dinitrodiphenylmethane with hexamethylene di-isocyanate (HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate (DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and 13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC).

Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

We have investigated the effect of solvent in the sol–gel process of tetraethylorthosilicate (TEOS) when di-n-butyltin dilaurate (DBTL) is used as polycondensation catalyst. Two sets of materials similar to those employed in the field of stone consolidation were prepared in the laboratory by using either protic or aprotic solvents: (1) xerogels from TEOS/DBTL, and (2) composites from TEOS/colloidal silica particles/DBTL. The results have shown that the solvent directly influences the aggregation pathway of the condensates. For a mixture of methyl ethyl ketone/acetone (aprotic solvents), gels with a higher degree of condensation were obtained. In the case of TEOS xerogels, the materials are essentially non-porous. Additionally, the incorporation of colloidal silica particles induces an important increase in porosity, which is even more dramatic when ethanol is used as solvent, through the formation of micro and mesoporous materials as the concentration of particles is increased. A TEOS polymerization pathway is suggested depending on which system of solvents is used. Various analytical techniques were used to characterize the materials obtained.

Polydimethylsiloxane‐Based Self‐Healing Materials

Polydimethylsiloxane-based self-healing is achieved through the tin-catalyzed polycondensation of phase-separated droplets. The catalyst is released into the crack plane when microcapsules containing a tin compound are ruptured by the advancing crack (see figure). This system greatly extends the capability of self-healing polymers by introducing a new, stable healing chemistry into a structural polymer matrix and may provide a route to self-healing in harsh and corrosive environments.

Platelet adhesion on a polyurethane surface grafted with a zwitterionic monomer of sulfobetaine via a Jeffamine spacer

AbstractA possible approach to improve the blood compatibility of poly(ether urethane)s (PU) involves the covalent attachment of key molecules on its surface. The purpose of the present study was to design and synthesise a novel non‐thrombogenic biomaterial by modifying the surface of the PU with a zwitterionic monomer of sulfobetaine via a Jeffamine spacer. In this study, sulfobetaine was grafted onto a PU surface through the following reaction steps: (1) The PU surface was activated with hexamethylene diisocyanate (HDI) in toluene at 50 °C in the presence of di‐n‐butyltin dilaurate (DBTDL) as a catalyst. The extent of the reaction was measured by ATR‐FTIR spectra; a maximum number of free NCO groups was obtained after a reaction time of 90 min. (2) One cap of Jeffamine was reacted with isocyanate groups bound on the surface, so Jeffamine was introduced. (3) The PU surface terminated by Jeffamine was recoupled with isocyanate groups by HDI. (4) The hydroxyl groups of 4‐dimethylamino‐1‐butanol (DMAB) or 2‐dimethylaminoethanol (DMAE) were allowed to react with the isocyanate groups capped on Jeffamine. (5) Sulfobetaines were constructed on the surface through the ring‐opening reaction between tertiary amine and 1,3‐propanesultone (PS). It was confirmed by ATR‐FTIR and XPS that the grafted surfaces were composed of sulfobetaine. The results of the contact‐angle measurements and water absorption showed that they were strongly hydrophilic. The results of this platelet adhesion experiment as a preliminary test showed that PU grafted with sulfobetaine has good blood compatibility featured by the low platelet adhesion. Copyright © 2004 Society of Chemical Industry

Platelet adhesive resistance of polyurethane surface grafted with zwitterions of sulfobetaine

A possible approach to improve the blood compatibility of poly(etherurethane)s (PU) involves the covalent attachment of key molecular on its surface. Recently, polymer tailed with zwitterions was found having good blood compatibility. The purpose of present study was to design and synthesis a novel nonthrombogenic biomaterial by modifying the surface of poly(etherurethane) with zwitterions of sulfobetaine via HDI spacer. The films of polyurethane were grafted with sulfobetaine by a three-step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate (HDI) in toluene at 50 °C in the presence of di-n-butyl tin dilaurate(DBTDL) as a catalyst. The extent of the reaction was measured by ATR-IR spectra; a maximum number of free NCO group was obtained after a reaction time of 2.5 h. In the second step, the primary amine group of N, N-diethylethylenediamine (DEA) or N, N-dimethylethylenediamine (DMA) was allowed to react in toluene with isocyanate groups bound on surface. In the third step, two kinds of sulfobetaines were formed in the surface through the ring-opening reaction between tertiary amine of DMA or DEA and 1,3- propanesultone (PS). The reaction process was monitored with ATR-IR spectra and XPS spectra. The wettability of films was investigated by water contact angle measurement. A platelet adhesion experiment was conducted as a preliminary test to confirm the improved blood compatibility of PU. The number of platelets adhering to PU decreased greatly compared to original after 1 h and 3 h of contact with human plate-rich plasma.

Studies on metal-containing copolyurethanes

Metal-containing copolyurethanes having ionic linkages in the main chain were synthesized by the polyaddition reaction of hexamethylene diisocyanate (HMDI) or toluene 2,4-diisocyanate (TDI) with 1:1 mixtures of divalent metal salts of mono(hydroxypentyl)phthalate, [M(HPP)] 2 (where M=Ca 2+, Cd 2+, Pb 2+ and Zn 2+), and diethylene glycol (DG) by using di- n-butyltin dilaurate (DBTDL) as catalyst. The prepared coployurethanes were characterized by FT-IR, 1H-NMR, 13C-NMR, elemental analysis, solubility, viscosity and X-ray diffraction studies. Thermal properties of the polymers were also studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The antibacterial activity of these polymers has also been investigated by agar diffusion method.

Platelet adhesion onto segmented polyurethane surfaces modified by carboxybetaine

Polyurethanes are widely used as blood-contacting biomaterials due to their good biocompatibility and mechanical properties. Nevertheless, their blood compatibility is still not adequate for more demanding applications. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of present study was to synthesize a novel nonthrombogenic biomaterial by modifying the surface of polyurethane with Zwitterions of carboxybetaine monomer. The films of polyurethane were grafted with two kinds of carboxybetaine by a three-step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate (HDI) in toluene at 50°C in the presence of di-n-butyl tin dilaurate (DBTDL) as a catalyst. The extent of the reaction was measured by ATR-FT-IR spectra; a maximum number of free NCO group was obtained after a reaction time of 90 min. In the second step, the hydroxyl group of N,N-dimethylethylethanolamine (DMEA) or 4-dimethylamino-1-butanol (DMBA) was allowed to react in toluene with isocyanate groups bound on surface. In the third step, carboxybetaines were formed in the surface through the ring-opening reaction between tertiary amine of DMEA or DMBA and β-propiolactone (PL). It was characterized by ATR-FT-IR and XPS that the grafted surfaces were composed of carboxybetaine. The results of the contact angle measurements showed that they were strongly hydrophilic. Platelet adhesion tests showed that films grafted carboxybetaine have good blood compatibility, as featured by the low platelet adhesion.

Thermal and Mechanical Properties of Sodium Lignosulfonate-based Rigid Polyurethane Foams Prepared with Three Kinds of Polyols

Rigid polyurethane (PU) foams were prepared by the following procedures. Sodium lignosulfonate (LS) was dissolved in diethylene glycol (DEG), triethylene glycol (TEG) or polyethylene glycol (average molecular weight, Mn200: PEG200). Rigid polyurethane foams were prepared by reacting the obtained solutions with polyphenyl polymethylene polydiisocyanate (MDI) in the presence of a silicone surfactant, di-n-butyltin dilaurate (DBTDL) and water. Thermal and mechanical properties of these polyurethanes (PU’s) were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and mechanical tests. Glass transition temperatures (Tg’s) of PU’s increased with increasing LS content and decreased with increasing Mn of ethylene glycol. Thermal degradation took place in two stages and temperatures (Td‘s) decreased with increasing LS content. Compressive stress at 10% strain (σ10) and compressive yielding stress (σy) increased with increasing apparent density (ρ) of PU’s.

STUDIES ON ZINC-CONTAINING POLYURETHANES AND POLYURETHANE-UREAS

ABSTRACT Zinc salt of mono(hydroxypentyl)phthalate [Zn[HPP]2] was synthesized by reacting 1,5-pentane diol, phthalic anhydride and zinc acetate. Zinc containing polyurethanes having ionic linkages in the main chain were synthesized by the polyaddition reaction of hexamethylene diisocyanate (HMDI) or toluylene 2,4-diisocyanate (TDI) with Zn[HPP]2, using di-n-butyltin dilaurate (DBTDL) as catalyst. Four different bisureas were prepared by reacting ethanolamine or propanolamine with HMDI or TDI. Zinc containing polyurethane-ureas were synthesized by reacting HMDI or TDI with 1:1 mixtures of Zn[HPP]2 and each of the bisureas. Zn[HPP]2 and the polymers were characterized by solubility, viscosity study, elemental analysis, FT-IR,1H-NMR,13C-NMR spectroscopy and thermogravimetric analysis (TGA).

STUDIES ON METAL-CONTAINING POLYURETHANES BASED ON DIVALENT METAL SALTS OF MONO(HYDROXYETHOXYETHYL)PHTHALATE

By reacting phthalic anhydride with excess of diethylene glycol and metal acetate, the metal salts of mono(hydroxyethoxyethyl)phthalate were prepared (metal = Cu2+, Mn2+ and Zn2+). Polyurethanes containing metal ions in the main chain were synthesized by reacting hexamethylene diisocyanate (HMDI) or tolulylene 2,4-diisocyanate (TDI) with Cu2+, Mn2+ and Zn2+ salts of mono(hydroxyethoxyethyl)phthalate using di-n-butyltin dilaurate (DBTDL) as catalyst. The prepared monomers and polyurethanes were characterized by FT-IR, 1H-NMR, 13C-NMR, UV spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), elemental analysis, solubility and viscosity studies. The antibacterial activity of these polyurethanes have also been investigated using agar diffusion method.

Unambiguous 13C‐NMR assignments for isocyanate carbons of isophorone diisocyanate and reactivity of isocyanate groups in Z ‐ and E‐stereoisomers

AbstractUnambiguous 13C‐NMR assignments for the primary (prim‐) and secondary (sec‐) isocyanate carbons of isophorone diisocyanate (IPDI) have been made by using two‐dimensional NMR measurements. On the basis of the assignments, relative reactivity of the prim‐ and sec‐isocyanate groups with n‐butanol was studied by quantitative 13C‐NMR analysis. The individual stereoisomers of IPDI (Z‐IPDI and E‐IPDI) and their equimolar mixture were reacted with n‐butanol (IPDI/n‐butanol = 2/1 molar ratio) at 50°C for 3 days. It was found that the sec‐NCO is about 1.6 times more reactive than the prim‐NCO in both Z‐ and E‐isomers. Reactivity of the E‐isomer was found to be slightly higher than that of the Z‐isomer. When di‐n‐butyltin dilaurate (DBTDL) was used as a catalyst, the reactivity of the sec‐NCO became about 12 times higher than that of the prim‐NCO with both isomers. In the case of 1,4‐diazabicyclo [2.2.2] octane (DABCO) catalyst, the prim‐NCO was 1.2 times more reactive than the sec‐NCO with both isomers.

Toxicological studies of a leachable stabilizer di-n-butyltin dilaurate(DBTL): effects on hepatic drug metabolizing enzyme activities.

Toxicological studies of a leachable stabilizer Di-n-butyltin dilaurate (DBTL) were undertaken. Effects of DBTL after 15 days oral exposure to rats were studied on brain and liver enzyme activities. A significant decrease in body weight gain of DBTL exposed rats were observed. No effect was observed in the activities of brain enzymes, succinic dehydrogenase, adenosine triphosphatase, acetylcholine esterase and monoamine oxidase. In liver, DBTL treatment resulted in a significant decrease in the activities of microsomal enzymes glucose-6-phosphatase, aminopyrine-N-demethylase, benzphetamine-N-demethylase, aniline hydroxylase, benzo(a)pyrene hydroxylase and also on cytochrome P-450 content, whereas no difference in the activities of mitochondrial enzymes, succinic dehydrogenase, Mg2+-adenosine triphosphatase as well as in the activity of lysosomal enzyme acid phosphatase was observed. Duration of exposure dependent increase in pentabarbital induced sleeping time was also observed. DBTL treatment produced an induction in heme oxygenase activity whereas the activity of -aminolevulinic acid synthetase remained unaltered. The results demonstrate that DBTL significantly affects the biotransformation mechanism and heme metabolism of hepatocytes.