Synthesis and Characterization of Hyperbranched Polyurethane

Aug 24, 2007 - Deconvolution of the FTIR spectra using Origin 6.0 software through ... ACS Sustainable Chemistry & Engineering 2013 1 (8), 910-918...
0 downloads 0 Views 528KB Size
Download PDF
6408

Ind. Eng. Chem. Res. 2007, 46, 6408-6416

Synthesis and Characterization of Hyperbranched Polyurethane-Urea/Silica Based Hybrid Coatings Kishore K. Jena and K. V. S. N. Raju* Organic Coatings and Polymers DiVision, Indian Institute of Chemical Technology, Hyderabad-500 007, India

A series of organic-inorganic hybrid coatings from hyperbranched polyurethanes (HBPU) were prepared using hyperbranched polyester and 3-aminopropyltriethoxysilane. Initially, isocyanate terminated HBPU prepolymers were synthesized from hyperbranched polyesters [prepared by the reaction of 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) with pentaerythritol, TMP, or glycerol as core moiety] with isophorone diisocyanate at NCO/OH ratio of 1.6:1 for 5 h at 70-80 °C. The partial excess NCO content of this prepolymer was reacted with 3-aminopropyltriethoxysilane in different concentrations. The remaining excess NCO completely reacted with atmospheric moisture. Fourier transform infrared (FTIR) spectroscopy was used for the structural analysis of HBPU hybrid coatings. Deconvolution of the FTIR spectra using Origin 6.0 software through Gaussian curve-fitting method was used to find out the changes and types of intermolecular H-bonding interactions in the hybrid films with the variation in concentration of sol-gel precursors added. The viscoelastic properties of the synthesized coatings were determined by dynamic mechanical thermal analysis (DMTA). 1. Introduction

Table 1. Various Reactants Used to Prepare the Hybrid HBPU Coatings along with Their Equivalent Ratios

Organic-inorganic hybrid materials have attracted much attention in recent years because of their distinct combination of properties of both inorganic and organic components. These materials provide transparent coatings with improved mechanical properties. These are prepared by sol-gel processes with its associated mild conditions with tunable structure.1-4 These are interesting materials for their potential wide-range applications, particularly in composites and coatings.5-9 Depending on the desired application, polymers with different mechanical properties can be obtained because of their versatility in the formulation variables. Additionally, because of the hybrid character, they present higher optical transparency, superior thermal and weathering resistance, and more excellent abrasion and impact resistance than traditional polymers like epoxies and polyurethanes.10-14 On the other hand, hyperbranched polymers can be used in formulating low volatile organic carbon (VOC) and highperformance coatings because of the availability of a large number of end groups, which can be tailored for different applications. Moreover, their properties are completely different compared to the linear polymers with the same molar mass, such as high chemical reactivity; low melt and solution viscosity; high solubility, miscibility, and reactivity due to their high segment density within the volume of a molecule; and lack of intermolecular entanglements. The high-density functional terminal groups on hyperbranched polymers also offer the potential for tailoring their structure through the conversion of end groups to chemically suitable moieties.15 These compounds replace linear polymers to reduce viscosity, increase reaction rate, and improve toughness because of their highly branched molecular structures. The aim of the present work is to prepare hyperbranched polyurethanes (HBPU) and incorporate the silica moieties and study their properties. 3-Aminopropyltriethoxysilane (APTES) was used as an inorganic precursor for the preparation of HBPUhybrid coatings. It is an organofunctional alkoxysilane monomer * Corresponding author. Tel.: +91-40-27193208. Fax: +91-4027193991. E-mail: [email protected]; [email protected].

NCO terminated PU (sample code) HBPU-C-PE

HBPU-C-TMP

HBPU-C-GLY

composition of NCO terminated PU and equivalent ratios PE/DMPA(1:4:8:16) NCO/OH ) 1.6:1

TMP/DMPA(1:3:6:12) NCO/OH ) 1.6:1

GLY/DMPA (1:3:6:12) NCO/OH ) 1.6:1

sample code of hybrid coatings HBPU-C-PE-Si5 HBPU-C-PE-Si10 HBPU-C-PE-Si20 HBPU-C-PE-Si30 HBPU-C-TMP-Si5 HBPU-C-TMP-Si10 HBPU-C-TMP-Si20 HBPU-C-TMP-Si30 HBPU-C-GLY-Si5 HBPU-C-GLY-Si10 HBPU-C-GLY-Si20 HBPU-C-GLY-Si30

that can undergo both the sol-gel polymerization of the alkoxy groups and the reaction with NCO functionality in the prepolymer to form a hybrid network with covalent bonds between organic and inorganic phases. The obtained hybrid coatings were characterized by Fourier transform infrared (FTIR), dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA) instruments. 2. Experimental Section 2.1. Materials. Pentaerythritol, trimethylol propane (TMP), 2,2-bis(methylol propionic acid) (bis-MPA), isophorone diisocyanate (IPDI: Z and E isomer in 3:1 ratio), dibutyltin dilaurate (DBTL), and 3-aminopropyltriethoxysilane (APTES) were purchased from Aldrich (Milwaukee, WI). Titanium tetraisopropoxide (TTIP) was purchased from Fluka Chemical Corp. (Ronkonkoma, NY). Glycerol (GLY) and dimethyl formamide (DMF) were procured from Qualigens (India). Methyl isobutyl ketone (MIBK) from Ranbaxy (Mumbai, India) and dimethyl formamide (DMF) and sulfur free toluene from S.D Fine Chemical (Mumbai, India) were used as received. The solvents were freed from moisture using 4 Å molecular sieves before use.

10.1021/ie0703181 CCC: $37.00 © 2007 American Chemical Society Published on Web 08/24/2007

Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007 6409 Scheme 1. Schematic Representation of the HBP and HBPU Preparations

2.2. Synthesis of Hyperbranched Polyester Polyol. A pseudo-one-step procedure was used to prepare hyperbranched polyester (HBP). This procedure involves sequential addition of a monomer, and each addition corresponds to the stoichiometric amount for the next theoretical generation. The polymers are identified by generation as second (B) and third (C) in accordance with the stoichiometric ratio between core and repeating units. Hyperbranched polyester of C, HB-C-PE, was synthesized by charging pentaerythritol and bis-MPA into a four-necked flask placed over an isomentel and equipped with mechanical stirrer, thermometer, nitrogen inlet, and Dean-Stark apparatus. The reactant mixture was slowly heated up to 190 °C, TTIP was added, and the reaction was continued for about 24 h under nitrogen atmosphere. The reaction was monitored periodically by checking the acid value and was stopped when the acid value reached below five. Similarly, third-generation HBPs of DMPA with TMP (HB-C-TMP) and glycerol (HB-C-GLY) as core were prepared. Here, HB stands for hyperbranched polyester; C stands for third generation; and PE, TMP, and GLY represent the core polyol.

2.3. Synthesis of NCO Terminated PU Prepolymer from Hyperbranched Polyol. HB-C-PE, HB-C-TMP, and HB-CGLY were reacted with IPDI at a NCO/OH ratio of 1.6:1 in a 250 mL four-necked round-bottomed flask equipped with a thermometer, dropping funnel, mechanical stirrer, and nitrogen inlet for 5 h at 70-80 °C. 2.4. Synthesis of Organic-Inorganic Hybrid Coatings. Organic-inorganic hybrid coatings were prepared from NCO terminated HBPU and APTES. The extra NCO groups in HBPU prepolymer, HBPU-C-PE based on NCO/NH2 ratio, were mixed with 5, 10, 20, and 30 wt % APTES, and the derived formulations were named as HBPU-C-PE-Si5, HBPU-C-PESi10, HBPU-C-PE-Si20, and HBPU-C-PE-Si30, respectively. Similarly, hybrid formulations of HBPU-C-TMP and HBPUC-GLY with 5, 10, 20, and 30 wt % of the extra NCO groups in HBPU prepolymer were mixed with APTES and named as HBPU-C-TMP-Si5, HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMP-Si30 and HBPU-C-GLY-Si5, HBPU-CGLY-Si10, HBPU-C-GLY-Si20, and HBPU-C-GLY-Si30, respectively. Here, HB represents hyperbranched polyester; PU stands for polyurethane urea; C stands for third generation; PE,

6410

Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007

Scheme 2. Preparation of Organic-Inorganic Hybrid HBPU Coatings by Sol-Gel Process

TMP, and GLY represent the core polyol; and Si5, Si10, Si20, and Si30 represent the wt % APTES. 2.5. Preparation of Organic-Inorganic Hybrid Films. The hybrid formulations were casted on tin foil using a film applicator. The supported films were kept at 25 °C and 50% RH for 60 days. The moisture-cured hybrid films were amalgamated and used for further characterization. Schemes 1and 2 show the steps involved in the synthesis of HBPU and hybrid HBPU coatings. Table 1 lists the various reactants used to prepare the different hybrid coatings along with their equivalent ratios. 2.6. Measurements. Melt viscosities of the HBP samples were determined using an Anton Paar Physica MCR 51 rheometer in Cup and Bop geometry from at 30, 40, 50, and 60 °C and from 0.01 to 100 s-1 shear rate. The MALDI mass spectra of HBP were recorded using a Kompact MALDI SEQ laser desorption time-of-flight mass spectrometer (Kratos Analytical, Manchester, U.K.) equipped with a pulsed nitrogen laser (λmax ) 337 nm, pulse width 3 ns). The matrix used was 2-(4-hydroxyphenylazo)benzoic acid (HABA) (Sigma, St. Louis, MO) of 10 mg/mL concentration in tetrahydrofuran (THF) solvent. The sample was prepared in THF solvent in 1 mg/mL concentration. Each sample for infrared analysis was prepared by casting the hybrid formulation onto a clean potassium bromide disc from a single drop of 1 wt % DMF solution. These samples were put into an oven at 60 °C for 6 h, under vacuum to completely remove the solvent, and later on kept at room temperature and humidity for 5 days before recording the FTIR spectra. Infrared data was obtained with the Thermo Nicolet Nexus 670 spectrophotometer between 4000 and 400 cm-1 with a resolution of 4 cm-1. Thirtytwo scans were averaged for each sample. The analysis and peak deconvolution of NsH and CdO bands were performed on Origin 6.0 software considering peaks as Gaussian with a number of iterations to get the best-fit Gaussian

peaks. The maximum error associated with the fit was estimated to be HBPU-C-TMP-Si30. 3.3.3. NsH Stretching Zone. Figure 4c shows the NsH region of FTIR spectra of different studied HBPU-hybrid films. The FTIR peak deconvolution of the NsH region of a representative sample HBPU-C-TMP-Si5 is shown in Figure 4d. The deconvoluted spectrum that comprised bands at 3202, 3349, and 3505 cm-1 corresponding to an overtone of deformation vibration of NsH group increased by Fermi resonance,26 hydrogen-bonded NsH, and free NsH, respectively, was observed. After deconvolution of the NsH stretching zone, it is not possible to give a general conclusion about the hydrogenbonding strength with the structural variables used. 3.4. DMTA Analysis. DMTA measurement gives information about the microstructure of a polymeric material. Figure 5a shows the E′ vs temperature plot of HBPU-hybrid coatings, i.e., HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMPSi30; and the corresponding tan δ vs temperature plots of HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMPSi30 are shown in Figure 5b. The Tg and height at tan δmax for HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMPSi30 are 125.7 °C, 0.72; 130.6 °C, 0.59; and 133.9 °C, 0.56, respectively. Figure 5c shows the E′ and tan δ vs temperature plots of HBPU-hybrid coatings HBPU-C-GLY-Si10 and HBPUC-GLY-Si20. The Tg and height at tan δmax for HBPU-C-GLYSi10 and HBPU-C-GLY-Si20 are 136.7 °C, 0.74 and 144.3 °C, 0.53, respectively. A comparison of dynamic mechanical properties among HBPU-C-TMP-Si20 and HBPU-C-GLY-Si20 shows that hybrid coatings prepared from glycerol based HBP

were harder than the TMP based HBP. This could be due to the formation of a larger amount of byproducts during the urithanication reaction of HB-C-GLY, which increased the cross-linked density in HBPU-C-GLY-Si20. The observed Tg values for the series HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, HBPU-C-TMP-Si30 and HBPU-C-GLY-Si10 and HBPU-CGLY-Si20 show that, with increasing APTES content in the hybrid films, the Tg and hardness increase. The loss tangent vs temperature plots of HBPU-C-PE-Si5, HBPU-C-TMP-Si5, and HBPU-C-GLY-Si5 hybrid coatings are shown in Figure 5d. The Tg and height at tan δmax for HBPU-C-TMP-Si5, HBPU-C-GLYSi5, and HBPU-C-PE-Si5 are 114.5 °C, 1.09; 116.0 °C, 0.75; and 120.8 °C, 0.58, respectively. These values clearly suggest that the flexibility of PE containing HBPU-hybrid coatings was less compared to those of glycerol and TMP containing hybrid coatings. This could be due to the availability of four functions in PE and, hence, a higher cross-link density in PE based hybrid coatings. The higher cross-link density of PE based hybrid coatings affected the loss tangent curves in two different ways. This occurs because the samples with higher cross-link density have higher Tg and the loss tangent peaks become broader with increasing cross-linking.27,28 The E′ values of these hybrid coatings at temperatures below 50 °C (>108 Pa) suggest the presence of good cross-linking and hardness. 3.5. Thermal Stability. Parts a and b of Figure 6 show the thermogravimetric and first derivative of TG curves of HB-CTMP and HB-C-GLY, respectively. The TG and DTG curves of HB-C-TMP and HB-C-GLY suggest a predominant singlestep decomposition profile with a small-tail decomposition step

6414

Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007

Figure 6. (a) TGA and (b) DTG thermograms of HB-C-TMP and HB-CGLY. Figure 8. (a) Thermogravimetric and (b) first-derivative TG thermograms of HBPU-hybrid coatings HBPU-C-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMP-Si30 prepared from TMP based third-generation polyesters.

Figure 7. (a) Thermogravimetric and (b) first-derivative TG thermograms of HBPU-hybrid coatings HBPU-C-PE-Si5, HBPU-C-TMP-Si5, and HBPUC-GLY-Si5 prepared from different third-generation polyesters.

at higher temperature. The onset temperature (Ton) corresponding to the maximum rate of weight loss (Tmax) and the endset decomposition temperature (Ten) of HB-C-TMP and HB-C-GLY are 270.2, 332.0, 365.5 °C; and 292.1, 339.5, and 372.0 °C, respectively, suggesting that HB-C-GLY is more stable against the thermal decomposition than HB-C-TMP. This could be due to the formation of side products, as explained earlier for

glycerol based hybrid coatings versus TMP based coatings. The characteristic thermal decomposition temperatures of HB-CTMP, HB-C-GLY, and their hybrid coatings are shown in Table 3. The TGA and DTG thermograms of hybrid coatings of HBPU-C-PE-Si5, HBPU-C-TMP-Si5, and HBPU-C-GLY-Si5 are shown in parts a and b of Figure 7, respectively. The characteristic decomposition data and the thermograms showed that initially hybrid coatings prepared from glycerol were stable up to 290 °C. A comparison of thermal stability among HBPUC-PE-Si5 and HBPU-C-TMP-Si5 suggests that the pentaerythritol based hybrid coating was more stable than the TMP based hybrid coating because of its high cross-linking density. Parts a and b of Figure 8 show the thermogravimetric and first derivative TG thermograms of hybrid coatings of HBPUC-TMP-Si10, HBPU-C-TMP-Si20, and HBPU-C-TMP-Si30 prepared from TMP and DMPA based third-generation polyester. The characteristic decomposition data suggest that the thermal stability of the hybrid films increases as the APTES content is increased.9,29 The TGA and DTG curve of hybrid coating of HBPU-C-GLY-Si10 prepared from glycerol and DMPA based third-generation polyester is shown in Figure 9. This is the representative case, where the TG experiment was carried out at 5 °C min-1 heating rate. The TG and DTG thermograms of all the hybrid coatings show two-step decomposition profiles. 3.6. Tensile Properties. Table 4 summarizes the tensile properties of the HBPU-APTES hybrid coatings. The strength increased and the elongation at the break decreased with the increasing APTES content. The tensile strength increased in the order of HBPU-C-TMP-Si10 < HBPU-C-TMP-Si20 < HBPUC-TMP-Si30, which is consistent with the DMTA results, suggesting that more interaction between the organic matrix and the APTES phase caused better mechanical strength. Moreover, the tensile strength obviously increased as the APTES content increased.

Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007 6415

Figure 9. TGA and DTG curves of HBPU-hybrid coating HBPU-C-GLY-Si10 prepared from glycerol based third-generation polyester at 5 °C min-1 heating rate.

4. Conclusions The versatility in designing HBP for the preparation of HBPU based hybrid coatings for high performance coating applications makes it a unique tool for obtaining a combination of properties like mechanical and thermal properties. In the present investigation, a third generation of HBPs was prepared by A2B + a core molecule approach, where A2B is DMPA and the core is TMP, pentaerythritol, or glycerol. The synthesized HBPs were characterized by MALDI that shows the cyclization of HBP, which takes place during the esterification process. These polyesters were used for the preparation HBPU, were partially reacted with APTES, and were cured with atmospheric moisture to prepare hybrid coatings. The band deconvolutions of the CdO and Ns H zones were carried out for a qualitative analysis of structureproperty relationships. The results suggest that the amount of hydrogen bonding and free urethane/urea groups of the hybrid coatings depends on the chemical structure of the HB polyester as well as the amount of APTES used. The observed Tg data from DMTA analysis suggest that Tg increases with increasing APTES content in the hybrid coatings. Hybrid coatings showed two-step decomposition profiles, and the thermal stability of these increases with increasing APTES content, showing good thermal stability and negligible weight loss up to 200 °C. We have demonstrated that APTES based hybrid coatings showed better thermal and mechanical property. Overall, our study shows that the APTES content can have a significant effect on the mechanical and thermal properties of hybrid coatings. Literature Cited (1) Zou, J.; Zhao, Y.; Shi, W.; Shen, X.; Nie, K. Preparation and Characters of Hyperbranched Polyester based Organic-Inorganic Hybrid Material Compared with Linear Polyester. Polym. AdV. Technol. 2005, 16, 55. (2) Frings, S.; Meinema, H. A.; van Nostrum, C. F.; van der Linde, R. Organic-Inorganic Hybrid Coatings for Coil Coating Application based on Polyesters and Tetraethoxysilane. Prog. Org. Coat. 1998, 33, 126. (3) Zou, J.; Shi, W.; Hong, X. Characterization and Properties of a Novel Organic-Inorganic Hybrid based on Hyperbranched Aliphatic Polyester prepared via Sol-Gel Process. Composites, Part A 2005, 36, 631. (4) Rekondo, A.; Fernandez-Berridi, M. J.; Irusta, L. Synthesis of Silanized Polyether Urethane Hybrid Systems. Study of the Curing Process through Hydrogen Bonding Interactions. Eur. Polym. J 2006, 42, 2069. (5) Nass, R.; Arpac, E.; Glaubitt, W.; Schmidt, H. J. Modeling of ORMOCER Coatings by Processing. J. Non-Cryst. Solids 1990, 121, 370. (6) Philipp, G.; Schmidt, H. J. New Materials for Contact Lenses Prepared from Si- and Ti-alkoxides by the Sol-Gel Process. J. Non-Cryst. Solids 1984, 63, 283. (7) Schmidt, H. J. Multifunctional Inorganic-Organic Composite SolGel Coatings for Glass Surfaces. J. Non-Cryst. Solids 1994, 178, 302.

(8) Innocenzi, P.; Sassi, A.; Brusatin, A.; Guglielmi, M.; Favretto, D.; Bertani, R.; Venzo, A.; Babonneau, F. A Novel Synthesis of Sol-Gel Hybrid Materials by a Nonhydrolytic/Hydrolytic Reaction of (3-Glycidoxypropyl)trimethoxysilane with TiCl4. Chem. Mater. 2001, 13, 3635. (9) Liu, Y. L.; Wu, C. S.; Chiu, Y. S.; Ho, W. H. Preparation, Thermal Properties, and Flame Retardance of Epoxy-Silica Hybrid Resins. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 2354. (10) Brennan, B. l.; Wikes, G. L. Structure-Property Behaviour of SolGel Derived Hybrid Materials: Effect of a Polymeric Acid Catalyst. Polymer 1991, 32, 733. (11) Ni, H.; Simonsick, W. J.; Skaja, A. D.; Williams, J. P.; Soucek, M. D. Polyurea/Polysiloxane Ceramer Coatings. Prog. Org. Coat. 2000, 38, 97. (12) Ni, H.; Skaja, A. D.; Soucek, M. D. Acid-Catalyzed MoistureCuring Polyurea/Polysiloxane Ceramer Coatings. Prog. Org. Coat. 2000, 40, 175. (13) Xu, J.; Shi, W.; Pang, W. Synthesis and Shape Memory Effects of Si-O-Si Crosslinked Hybrid Polyurethanes. Polymer 2006, 47, 457. (14) Chen, Y.; Zhou, S.; Gu, G.; Wu, L. Microstructure and Properties of Polyester-based Polyurethane/Titania Hybrid Films Prepared by SolGel Process. Polymer 2006, 47, 1640. (15) Asif, A.; Shi, W. UV Curable Waterborne Polyurethane Acrylate Dispersions based on Hyperbranched Aliphatic Polyester: Effect of Molecular Structure on Physical and Thermal Properties. Polym. AdV. Technol. 2004, 15, 669. (16) Feast, W. J.; Keeney, A. J.; Kenwright, A. M.; Parker, D. Synthesis, Structure and Cyclics content of Hyperbranched Polyesters. Chem. Commun. 1997, 1749. (17) Burgath, A.; Sunder, A.; Frey, A. Role of Cyclization in the Synthesis of Hyperbranched Aliphatic Polyesters. Macromol. Chem. Phys. 2000, 201, 782. (18) Parker, D.; Feast, W. J. Synthesis, Structure, and Properties of CoreTerminated Hyperbranched Polyesters based on Dimethyl 5-(2-Hydroxyethoxy)isophthalate. Macromolecules 2001, 34, 5792. (19) Hsieh, T. T.; Tiu, C.; Simon, G. P. Melt Rheology of Aliphatic Hyperbranched Polyesters with Various Molecular Weights. Polymer 2001, 42, 1931. (20) Hsieh, T. T.; Tiu, C.; Simon, G. P. Rheological Behaviour of Polymer Blends Containing only Hyperbranched Polyesters of Varying Generation Number. Polymer 2001, 42, 7635. (21) Nunez, C. M.; Chiou, B. S.; Andrady, A. L.; Khan, S. A. Solution Rheology of Hyperbranched Polyesters and Their Blends with Linear Polymers. Macromolecules 2000, 33, 1720. (22) Narayan, R.; Chattopadhyay, D. K.; Raju, K. V. S. N.; Mallikarjuna, N. N.; Jawalkar, S. S.; Aminabhavi, T. M. Viscosity Behavior of Hydroxylated and Acetoacetylated Polyesters. J. Appl. Polym. Sci. 2006, 100, 2422. (23) Wang, L. F.; Ji, Q.; Glass, T. E.; Ward, T. C.; McGrath, J. E.; Muggli, M.; Burns, G.; Sorathia, U. Synthesis and Characterization of Organosiloxane modified Segmented Polyether Polyurethanes. Polymer 2000, 41, 5083. (24) Chattopadhyay, D. K.; Mishra, A. K.; Sreedhar, B.; Raju, K. V. S. N. Thermal and Viscoelastic Properties of Polyurethane-Imide/Clay Hybrid Coatings. Polym. Degrad. Stab. 2006, 91, 1837. (25) Mishra, A. K.; Chattopadhyay, D. K.; Sreedhar, B.; Raju, K. V. S. N. FT-IR and XPS Studies of Polyurethane-Urea-Imide Coatings. Prog. Org. Coat. 2006, 55, 231.

6416

Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007

(26) Romanova, V.; Begishev, V.; Karmanov, V.; Kondyurin, A.; Maitz, M. F. Fourier Transform Raman and Fourier Transform Infrared Spectra of Crosslinked Polyurethane-Urea Films Synthesized from Solutions. J. Raman Spectrosc. 2002, 33, 769. (27) Tai, H.; Sargienko, A.; Silverstein, M. S. Organic-Inorganic Networks in Foams from High Internal Phase Emulsion Polymerizations. Polymer 2001, 42, 4473. (28) Asif, A.; Shi, W.; Shen, X.; Kangming, N. Physical and Thermal Properties of UV Curable Waterborne Polyurethane Dispersions incorporating Hyperbranched Aliphatic Polyester of Varying Generation Number. Polymer 2005, 46, 11066.

(29) Macan, J.; Ivankovic, H.; Ivankovic, M.; Mencer, H. J. Synthesis and Characterization of Organic-Inorganic Hybrid Based on Epoxy Resin and 3-Glycidyloxypropryltrimethoxysilane. J. Appl. Polym. Sci. 2004, 92, 498.

ReceiVed for reView March 1, 2007 ReVised manuscript receiVed July 19, 2007 Accepted July 19, 2007 IE0703181