Transparent Nanostructured Thermoset Composites Containing Well

Dec 7, 2010 - (SEO) block copolymer used as templating agent and titanium dioxide (TiO2) ... Ternary systems showed good dispersion of synthesized...
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Transparent Nanostructured Thermoset Composites Containing Well-Dispersed TiO2 Nanoparticles Junkal Gutierrez, Agnieszka Tercjak,* and In˜aki Mondragon* ‘Materials + Technologies’ Group, Dpto. Ingenierı´a Quı´mica y M. Ambiente, Escuela Polite´cnica, UniVersidad Paı´s Vasco/Euskal Herriko Unibertsitatea, Pza. Europa 1, 20018 Donostia-San Sebastian, Spain ReceiVed: July 29, 2010; ReVised Manuscript ReceiVed: NoVember 15, 2010

Novel inorganic-organic nanostructured thermosetting composites based on poly(styrene-b-ethylene oxide) (SEO) block copolymer used as templating agent and titanium dioxide (TiO2) nanoparticles synthesized via sol-gel were prepared. The morphologies generated in the binary and ternary epoxy-based systems were studied using atomic force microscopy (AFM). Ternary systems showed good dispersion of synthesized nanoparticles even for a high amount of sol-gel and simultaneously maintained nanostructural ordering of the cured block copolymer/epoxy-based system due to the capability of SEO block copolymer for self-assembling at nanoscale. Additionally, the conductive properties of TiO2 nanoparticles embedded in nanostructured thermosetting composites were confirmed using electrostatic force microscopy (EFM) measurements. High UV-shielding efficiency was achieved by the incorporation of the TiO2 nanoparticles without losing the high-visible light transparency of the ternary systems. This study can open a novel pathway for generation of new transparent multifunctional advanced thermosetting materials with tunable properties controlled varying the ratio between inorganic and organic components. Introduction Thermosetting materials based on epoxy resins, especially thermoset systems modified with block copolymers, have been widely investigated during the past decade1-11 due to the fact that block copolymers offer the possibility for controlling selfassembling at the nanometer scale on the resulting systems, thus allowing the properties of the achieved materials to be optimized. Solely in few works, synthesis and characterization of inorganic nanoparticle/epoxy nanocomposites have been reported. The interest to develop this kind of systems relies upon the unique opportunity to combine mechanical, optical, magnetic, and optoelectronic properties.12-15 These properties can be tuned varying the concentration, size, or type of nanoparticles. As it is well-known, the major problem in preparation of this kind of nanocomposites is related to achieving homogeneous dispersion of inorganic nanoparticles in the epoxy matrix.12 Nowadays, in order to reach new requirements in nanotechnology, ternary thermosetting systems modified with inorganic nanoparticles and block copolymers have attracted attention.16-18 Nanostructured thermosetting systems designed using different block copolymers are challenging to obtain multifunctional hybrid inorganic/organic materials, since block copolymers can act as a template for the incorporation of inorganic nanoparticles. In the case of these multifunctional thermosetting systems modified with nanoparticles, the main objective is the control of the distribution and size of synthesized nanoparticles due to these parameters limit possible applications of the designed materials.19,20 Additionally, many researchers are currently looking for selective confinement of nanoparticles in one of the microphase separated domains playing with the capability of block copolymers to nanostructuring the epoxy resins. On the other hand, introduction of titanium dioxide nanoparticles into * To whom correspondence should be addressed. E-mail: agnieszka.tercjaks@ ehu.es (A.T.); [email protected] (I.M.).

the multifunctional materials provides new interesting properties such as dielectric, optical, or catalytic.12,16,17 In the present work, the ability of the block copolymer for both nanostructuring of epoxy systems and selective dispersion of nanoparticles has allowed us to obtain advanced multifunctional hybrid nanostructured thermosetting materials. Poly(styreneb-ethylene oxide) block copolymers have been used as a template for selective location of titanium dioxide (TiO2) nanoparticles, using the procedure published by Sun et al.,21 Cheng et al.,22 and Gutierrez et al.23-25 Bisphenol-A-type epoxy resin modified with amphiphilic poly(styrene-b-ethylene oxide) block copolymer (SEO) and titanium dioxide nanoparticles synthesized via sol-gel was used. The in situ sol-gel process allowed one to confine titanium nanoparticles at the interface between the PEO block/epoxyrich phase and microphase separated PS block domains. Sol-gel precursor self-associated reactions generated a hydrophilic inorganic network which was able to interact with the epoxyrich phase, leading to titanium nanoparticles embedded in the thermosetting system.13,14 Electrostatic force microscopy (EFM) was used in order to study the conductive properties of prepared hybrid inorganic/organic nanostructured thermosetting systems. This technique became a powerful tool for investigating qualitatively conductive properties at the nanoscale, taking into account that EFM measurements allowed the electric field gradient distribution above the sample surface to be detected.26-28 Experimental Section Materials. Poly(styrene-b-ethylene oxide) block copolymer (SEO) (MnPS ) 58 600 g mol-1, MnPEO ) 31 000 g mol-1, I ) 1.03 for both blocks) from Polymer Source, Inc., was used as received. For the generation of titanium dioxide nanoparticles via sol-gel synthesis, titanium isopropoxide (Ti(OCH(CH3)2)4, TTIP) was obtained from Aldrich and used as the precursor for nanoparticles. Isopropanol (IPA), hydrochloric acid (HCl, 37%),

10.1021/jp1070902  2010 American Chemical Society Published on Web 12/07/2010

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Figure 1. TM-AFM images (5 µm × 5 µm) of the 40 wt % SEO-(DGEBA/MCDEA) system. The inset at the top left corresponds to the digital image of transparency.

and toluene were analytical grade. A diglicydylether of bisphenol A epoxy monomer (DGEBA) (DER 332, purchased from Dow Chemical) was used. It has an epoxy equivalent around 175 g/mol and an average number of hydroxyl groups per two epoxy groups of n ) 0.03. This epoxy resin was cured with a stoichiometric amount of an aminic hardener, 4,4′-methylenebis(3-chloro 2,6-diethylaniline) (MCDEA), supplied by Lonza. Sol-Gel Synthesis. Titanium sol-gel solution (SG) was obtained according to the procedure published by Sun et al.21 and Cheng et al.22 The sol-gel solution was prepared mixing IPA (5 mL), TTIP (0.125 mmol), HCl (0.125 mmol), and toluene (5 mL) under vigorous stirring for 1 h. Blending Protocol. The block copolymer/epoxy cured system was prepared in the following way: first, SEO block copolymer and DGEBA resin were dissolved in toluene and the resultant mixture was heated at 80 °C in an oil bath until complete solvent removal was achieved. Once the solvent was removed, the curing agent, MCDEA, was added to the mixture and a homogeneous binary system was obtained. In the case of ternary systems, the desired amount of sol-gel solution was added to DGEBA resin and mixed at 80 °C for 10 min. Then, SEO block copolymer and toluene were added to the mixture and after evaporation of toluene MCDEA was added. Finally, all samples (binary and ternary systems) were degassed in a vacuum and cured at 190 °C for 4 h. Here, it should be pointed out that, as it is well-known from the literature,5,7,10,29 the mixture of the SEO block copolymer, DGEBA and MCDEA, was homogeneous before the polymerization process. Methods. The dispersion of TiO2 nanoparticles and morphology of investigated binary and ternary thermosetting systems were studied by atomic force microscopy (AFM). AFM measurements were performed in tapping mode using a Nanoscope IIIa (Multimode from Digital Instruments) equipped with an integrated silicon tip/cantilever having a resonance frequency of ∼300 kHz. Scan rates ranged from 0.7 to 1.2 Hz s-1. The flat surfaces of the investigated systems were obtained by cutting with a diamond knife using a Leica Ultracut R ultramicrotome. Electrostatic force microscopy was used to study the conductivity capability of TiO2 nanoparticles in the nanostructured thermosetting systems. These measurements were performed using the same scanning probe microscopy operating in this case in the lift mode (lift height was ∼300 nm) in ambient conditions and equipped with an integrated Co/Cr-coated MESP

tip having a resonance frequency around 75 kHz. The secondary imaging mode derived from the tapping mode that measures the electric field gradient distribution above the sample surface was detected by applying a voltage to the cantilever tip. Quantitative voltage measurements were made up of the relative voltages within a single image. Differential scanning calorimetry (DSC) measurements were performed using a Perkin-Elmer DSC-7 calorimeter with nitrogen flux. Curing was performed in aluminum pans containing a sample weight of around 7 mg. The curing behavior of the different epoxy-based systems was analyzed by means of isothermal experiments performed at 190 °C for 130 min. All samples were tested immediately after preparation. Dynamic scans were performed from 0 to 220 °C at heating rates of 10 °C min-1. The values of the glass transition temperature (Tg) were determined at the end-set point of the change in heat capacity. UV-vis absorption spectra were obtained on a Jasco V-630 spectrophotometer by scanning between 200 and 1000 nm. Finally, in order to analyze the photochemical stability of the synthesized epoxy-based composites, samples were irradiated at different times using UV light (254 nm, XX-15S, UPV Inc.). Results and Discussion Since the cured thermosetting systems were prepared in a parallelepiped mold of 1.5 mm thickness, all results are referred to the bulk behavior. In Figure 1, the morphology generated in the 40 wt % SEO-(DGEBA/MCDEA) thermosetting system studied using AFM is shown. The investigated binary system was transparent, thus indicating the absence of macroscopic phase separation (digital image inset in Figure 1). AFM height and phase images clearly indicated the existence of microphase separation (dark areas) in the epoxy matrix (bright areas). Since the PEO block of the SEO amphiphilic block copolymer is miscible with the epoxy matrix,30,31 segregation of the PS blockrich phase takes place during network formation. Consequently, the separated phase corresponds to PS block-rich domains. This system shows a hexagonally ordered structure where PS block cylinders (dark domains) are mainly perpendicularly oriented. The size of the microphase separated PS domains was around 60 nm in diameter. Although perpendicular is the preferential disposition, it should be pointed out that parallelly oriented cylinders also appeared in some regions of the system. Figure 2a and c shows AFM height and phase images of the 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA) and 40 wt %

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Figure 2. TM-AFM images (5 µm × 5 µm) of the epoxy matrix modified with 40 wt % (block copolymer:sol-gel) varying SEO:SG ratio: (a) 70:30; (b) high magnification of part a; (c) 30:70; (d) high magnification of part c. The inset at the top left corresponds to the digital image of transparency.

(30:70/SEO:SG)-(DGEBA/MCDEA) composites, respectively. All 40 wt % (SEO:SG)-based epoxy composites were transparent, as can be observed in the inset at the top left of each image, thus indicating the absence of macroscopic phase separation. AFM images corresponding to the 40 wt % (70:30/SEO: SG)-(DGEBA/MCDEA) composite show, similarly to the 40 wt % SEO-(DGEBA/MCDEA) system, hexagonally packed cylinder morphology where PS cylinders are arranged parallel and perpendicular. It should be noted that in this case welldispersed bright spots appearing along the sample surface correspond to TiO2 nanoparticles, taking into account that the spherical TiO2 nanoparticles are the hardest component of these

systems.12 These small nanoparticles appeared in the interface between the gray PEO-modified epoxy matrix and microphase separated PS block domains. A high magnification image (Figure 2b) clearly shows the bright TiO2 nanoparticles and the different location (parallel and perpendicular) of PS block cylinders with a size distribution between 50 and 70 nm in diameter homogenously dispersed in the continuous epoxy matrix. Moreover, Figure 2c shows AFM (height and phase) images and a corresponding digital image of transparency for the 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) composite. In this system, the ratio between block copolymer and sol-gel was changed, increasing the inorganic content of the sample. AFM

Transparent Nanostructured Thermosetting Composites images (height and phase) show uniformly dispersed spherical PS block domains with an average diameter of ∼50 nm in the continuous epoxy matrix. Simultaneously, the AFM height image clearly shows well-dispersed individual TiO2 nanoparticles (brightest spots) embedded in the epoxy matrix. In this case, with increasing sol-gel content, a higher amount of uniformly distributed TiO2 nanoparticles was detected in the epoxy-rich matrix if compared with the 40 wt % (70:30/SEO: SG)-(DGEBA/MCDEA) composite. It is worth noting that TiO2 nanoparticles in the hybrid inorganic-organic nanostructured thermosetting systems are not clearly detected in the AFM phase image. This phenomenon can be explained taking into account that the inorganic nanoparticles can interact with the epoxy-rich phase and consequently appeared covered by this organic phase. The high magnification AFM phase image (1 µm × 1 µm) of the 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) composite (Figure 2d) was performed in order to clarify the different microphases and location of TiO2 nanoparticles. This image shows clearly PS block dark domains microphase separated from the light continuous PEO block/epoxy-rich phase. Additionally, one can easily detect the well-dispersed brightest spots attributed to TiO2 nanoparticles, which are preferentially confined at the interface between the epoxy-rich matrix and microphase separated PS block domains. This phenomenon is related to the strong interactions between the epoxy matrix containing PEO block chains and the synthesized hydrophilic sol-gel network. As can be clearly observed, a narrow distribution of the size of TiO2 nanoparticles was obtained with a diameter around 10-20 nm. The curing behavior of binary and ternary systems was studied by DSC. Isothermal DSC thermograms for 40 wt % SEO-(DGEBA/MCDEA), 40 wt % (SEO:SG)-(DGEBA/ MCDEA) with different block copolymer and sol-gel contents, as well as neat DGEBA/MCDEA are shown in Figure 3a. The addition of 40 wt % SEO block copolymer into the neat DGEBA/MCDEA system led to longer reaction times, which is possibly due to the dilution effect related to the addition of SEO block copolymers into thermosetting systems.30,32 Moreover, the introduction of low sol-gel content (70:30/SEO:SG) into the binary SEO-(DGEBA/MCDEA) system did not change the curing reaction time significantly if compared to the thermosetting system modified only with 40 wt % SEO. Nevertheless, it should be pointed out that the dilution effect of the block copolymer in the composite was limited if compared with the 40 wt % SEO-(DGEBA/MCDEA) system, since the ternary composite contains less content of SEO block copolymer. On the other hand, the introduction of a high amount of inorganic component (30:70/SEO:SG) to the neat epoxy system led to a significant decrease of curing time. The curing time of the 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) composite shifted to shorter times even if compared to the neat DGEBA/ MCDEA system. In this case, the curing reaction was strongly affected by the catalytic effect related to possible interactions between epoxy resin and sol-gel. As it is well-known from the literature, the addition of hydroxyl groups, in this case sol-gel, into the epoxy system significantly promotes the curing reaction process.18,33 The effect of both SEO block copolymer and sol-gel content on the glass transition temperature of the epoxy-rich phase when compared to the Tg value of the neat DGEBA/MCDEA system was also investigated by DSC. As can be observed in Figure 3b, in the case of the 40 wt % SEO-(DGEBA/MCDEA) system, the Tg value of the epoxy-rich phase shifted to lower

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Figure 3. (a) Isothermal DSC thermograms recorded at 190 °C of investigated systems. (b) Dynamic DSC scans of cured systems recorded at 10 °C/min in nitrogen atmosphere.

temperature with respect to the Tg value of the neat DGEBA/ MCDEA system, which confirms the miscibility between the epoxy resin and the PEO block of the block copolymer. These results are in good agreement with the AFM results discussed above. As expected, Tg values of the epoxy-rich matrix in the ternary epoxy-based composites were higher when compared to the epoxy system modified only with 40 wt % SEO block copolymer. This effect once more is related to the strong interaction between epoxy resin and sol-gel. Here, it should be pointed out that the Tg corresponding to the PS-rich phase was not detected probably because of the small amount of PS block with respect to the whole amount of the systems. In order to confirm the conductive properties of the TiO2 nanoparticles embedded in nanostructured thermosetting composites, EFM measurements were performed. The EFM phase image of the 40 wt % SEO-(DGEBA/MCDEA) thermosetting system with different negative and positive bias voltages applying to the conductive EFM tip and the AFM height image taken simultaneously are shown in Figure 4. In the case of the AFM height image, the obtained nanostructure was in good agreement with the AFM results described above. EFM measurements for the epoxy system modified with 40 wt % SEO block copolymer demonstrate that no charge domains were detected on the surface regardless of both the value and the sign of the applied bias voltage. Taking this into account, one can conclude that under the measurement conditions the 40 wt % SEO-(DGEBA/MCDEA) composite does not respond to the applied voltage.

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Figure 4. TM-AFM height image (5 µm × 5 µm) and EFM phase image (5 µm × 5 µm) applying a negative and positive bias for the 40 wt % SEO-(DGEBA/MCDEA) system. Figure 6. UV-vis transmittance spectra of investigated systems. Inset: details of UV-vis transmittance spectra.

Figure 5. EFM phase images (5 µm × 5 µm) applying a negative and positive bias for the (a) 40 wt % (70:30/SEO:SG)-(DGEBA/ MCDEA) and (b) 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) systems.

Figure 5 shows EFM phase images of ternary nanostructured thermosetting systems with different bias voltages applying to the EFM tip. The EFM phase image for the 40 wt % (70:30/ SEO:SG)-(DGEBA/MCDEA) composite shows that, while a bias of 0 V is applied to the tip (middle part of the EFM phase image), any charge domains are detected on the surface of the investigated sample. Moreover, the same response was detected increasing both negative and positive bias voltage. It is worth noting that the EFM phase image was almost completely dark. Thus, only a few low contrast bright domains corresponding to the TiO2 nanoparticles were detected when the highest bias voltage value was applied. Here, it should be pointed out that low conductive response is related to the sol-gel content in the 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA) composite, since the investigated system contains a small amount of TiO2 nanoparticles. The same measurements were performed for the 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) composite. As seen in Figure 5b, the EFM phase image with 0 V bias voltage applying to the EFM tip (middle part) confirms that no charged domains were detected on the surface of the sample. On the contrary, increasing both positive (upper part) and negative bias voltage (bottom part) allows the detection of conductive bright zones in the EFM phase image. Higher contrast in the EFM phase image was detected with increasing both positive and negative bias voltage values. Taking into account that 40 wt % SEO-(DGEBA/MCDEA) was uncharged composite, the obtained results suggested that TiO2 nanoparticles maintain conductive properties regardless of the sign of the bias voltage applied to the EFM tip. Thus, only ternary systems respond to electrical stimuli. The incorporation of TiO2 nanoparticles to the nanostructured thermosetting systems provides conductive properties that can open the

door to a wide range of possible applications in electronic nanodevices. Taking into account the optical properties of TiO2 nanoparticles and the actual interest to develop transparent and UVfiltering composites, UV-vis measurements were performed. The UV-vis transmittance spectra of neat DGEBA/MCDEA and 40 wt % SEO-(DGEBA/MCDEA) and 40 wt % (SEO: SG)-(DGEBA/MCDEA) composites are shown in Figure 6. As expected, the neat DGEBA/MCDEA system possesses good visible light transmittance and poor UV-light shielding properties. In the case of 40 wt % SEO-(DGEBA/MCDEA), the addition of the block copolymer led to degradation of optical properties in the UV range. On the contrary, in the same range, transmittances of the ternary systems (40 wt % (70:30/SEO: SG)-(DGEBA/MCDEA)and40wt%(30:70/SEO:SG)-(DGEBA/ MCDEA)) were close to zero, thus indicating that the addition of TiO2 nanoparticles provokes an increase of UV absorption. Consequently, hybrid inorganic/organic nanostructured thermosetting composites are able to shield the UV light. Here, it should be pointed out that the 40 wt % (30:70/SEO:SG)-(DGEBA/ MCDEA) system showed higher UV-light shielding properties compared to the 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA) system. This phenomenon is related to the higher amount of TiO2 nanoparticles, since increasing the TiO2 nanoparticle content leads to a decrease in the transmittance and consequently provokes higher UV-light shielding efficiency. Besides the UV-shielding property, generated hybrid inorganic/ organic nanostructured thermosetting composites are transparent in the visible range, as shown in both the UV-vis spectra (Figure 6) and the digital images in Figure 2. At a relatively low visible light wavelength (600 nm), the transmittance of neat DGEBA/MCDEA, 40 wt % SEO-(DGEBA/MCDEA), and two ternary systems, 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA) and 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA), was 65, 58, 41, and 60%, respectively. These results indicate that the composites possess a somewhat lower visible light transmittance compared to the neat DGEBA/MCDEA system. Here, it should be pointed out that, in the high visible range, the transmittance of the 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA) system reached almost the same level as the neat DGEBA/MCDEA system. This phenomenon can be related to the strong interaction between epoxy resin and sol-gel. Hydroxyl groups of the sol-gel solution are able to polycondense with the hydroxyl groups of epoxy, leading to higher compatibility between both components. To summarize, TiO2 nanoparticles clearly enhance the UV-shielding efficiency of the inorganic/organic nanostruc-

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J. Phys. Chem. C, Vol. 114, No. 51, 2010 22429 photochemical stability after exposure to UV light irradiation. Thus, it seems that this system is more photochemically stable. This behavior can be related to the addition of a high amount of TiO2 nanoparticles to the epoxy system. Conclusions Novel transparent multiphase nanostructured thermosetting composites with well-dispersed TiO2 nanoparticles were developed using poly(styrene-b-ethylene oxide) as a templating agent. Self-organization of the designed materials and the fact that the sol-gel network interacts with both epoxy resin and the PEO block of the block copolymer results in good dispersion of generated TiO2 nanoparticles, which located mainly in the interface between the PEO block/epoxy-rich and microphase separated PS block domains. The neat thermosetting system modified with high sol-gel content also led to good dispersion of TiO2 nanoparticles in the nanostructured epoxy-based matrix. Designed thermosetting composites containing both TiO2 nanoparticles and SEO block copolymer can open a new strategy for preparation of well-defined transparent multifunctional thermosetting materials which possess both electrical properties and high UV-shielding efficiency, thus leading to materials with possible applications in the field of nanotechnology.

Figure 7. (a) Changes in the level of transmittance of investigated systems at 600 nm upon UV light irradiation. (b) Digital images of transparency. (f) DGEBA/MCDEA, (9) 40 wt % SEO-(DGEBA/ MCDEA), (2) 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA), and (b) 40 wt % (30:70/SEO:SG)-(DGEBA/MCDEA).

tured thermosetting systems without losing high-visible light transparency. Additionally, in order to study the photochemical stability of the samples, generated epoxy-based systems were exposed to UV light. UV-vis spectra of the investigated systems as a function of the UV light irradiation time are shown in Figure 7a. To monitor the UV light irradiation effect on the photochemical stability, the transmittance at a relatively low visible light wavelength (600 nm) has been plotted versus time. For all investigated systems, UV light irradiation resulted in a slight decrease of the transmittance values. Here, it should be noted that the relation between the transmittance of the samples remained constant. The appearance of the investigated samples before and after 80 h of UV light irradiation is shown in Figure 7b. As can be observed in the digital images, the UV light degradation process resulted in a slight yellowing of the samples. The photochemical stability was also studied by FTIR spectroscopy. FTIR spectra of neat DGEBA/MCDEA, 40 wt % SEO-(DGEBA/MCDEA) and two ternary systems, 40 wt % (70:30/SEO:SG)-(DGEBA/MCDEA) and 40 wt % (30:70/ SEO:SG)-(DGEBA/MCDEA), were recorded as a function of UV light irradiation time (not shown here). It is worth noting that neither neat epoxy nor epoxy-based composites showed significant changes in the corresponding spectra after 80 h of UV light exposure time. However, as expected, the unique modifications were essentially in the carbonyl absorption areas. For all investigated systems, the FTIR band associated with this group increased with increasing UV light exposure time. According to UV-vis and FTIR results, the 40 wt % (30: 70/SEO:SG)-(DGEBA/MCDEA epoxy system shows higher

Acknowledgment. Financial support from the Basque Country Government in the frame of Grupos Consolidados (IT-36507) and ETORTEK/inanoGUNE project and from the Spanish Ministry of Education and Science (MAT2009-12832) is gratefully acknowledged. Additionally, J.G. thanks Eusko Jaurlaritza/Gobierno Vasco (Programas de becas para formacio´n y perfeccionamiento de personal investigador) and A.T. acknowledges MICINN for Ramo´n y Cajal program. Moreover, we are grateful to the ‘Macrobehavior - Mesostructure Nanotechnology’ SGIker unit of the UPV/EHU. References and Notes (1) Hillmyer, M. A.; Lipic, P. M.; Hadjuk, D. A.; Almdal, K.; Bates, F. S. J. Am. Chem. Soc. 1997, 119, 2749–2750. (2) Ritzenthaler, S.; Court, F.; David, L.; Girard-Reydet, E.; Leibler, L.; Pascault, J. P. Macromolecules 2002, 35, 6245–6254. (3) Ritzenthaler, S.; Court, F.; David, L.; Girard-Reydet, E.; Leibler, L.; Pascault, J. P. Macromolecules 2003, 36, 118–126. (4) Maiez-Tribut, S.; Pascault, J. P.; Soule, E. R.; Borrajo, J.; Williams, R. J. J. Macromolecules 2007, 40, 1268–1273. (5) Meng, F.; Zheng, S.; Zhang, W.; Li, H.; Liang, Q. Macromolecules 2006, 39, 711–719. (6) Ocando, C.; Serrano, E.; Tercjak, A.; Pen˜a, C.; Kortaberria, G.; Calberg, C.; Jerome, R.; Carrasco, P. M.; Mecerreyes, D.; Mondragon, I. Macromolecules 2007, 40, 4068–4074. (7) Meng, F.; Xu, Z.; Zheng, S. Macromolecules 2008, 41, 1411–1420. (8) Tercjak, A.; Serrano, E.; Garcia, I.; Mondragon, I. Acta Mater. 2008, 56, 5112–5122. (9) Serrano, E.; Martin, M. D.; Tercjak, A.; Pomposo, J. A.; Mecerreyes, D.; Mondragon, I. Macromol. Rapid Commun. 2005, 26, 982–985. (10) Serrano, E.; Tercjak, A.; Kortaberria, G.; Pomposo, J. A.; Mecerreyes, D.; Zafeiropoulos, N. E.; Stamm, M.; Mondragon, I. Macromolecules 2006, 39, 2254–2261. (11) Tercjak, A.; Serrano, E.; Mondragon, I. Macromol. Rapid Commun. 2007, 28, 937–941. (12) Sangermano, M.; Malucelli, G.; Amerio, E.; Bongiovanni, R.; Priola, A.; Di Gianni, A.; Voit, B.; Rizza, G. Macromol. Mater. Eng. 2006, 291, 517–523. (13) Chau, J. L. H.; Tung, Ch.-T.; Lin, Y. M.; Li, A. K. Mater. Lett. 2008, 62, 3416–3418. (14) Amerio, E.; Sangermano, M.; Malucelli, G.; Priola, A.; Voit, B. Polymer 2005, 46, 11241–11246. (15) Chiang, Ch.-L.; Ma, Ch.-Ch. M. Eur. Polym. J. 2002, 38, 2219– 2224. (16) Tercjak, A.; Gutierrez, J.; Ocando, C.; Mondragon, I. Langmuir 2010, 26, 4296–4302. (17) Tercjak, A.; Gutierrez, J.; Peponi, L.; Rueda, L.; Mondragon, I. Macromolecules 2009, 42, 3386–3390.

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