Structural effects of TiO2 nanoparticles in photocurable ladder-like polysilsesquioxane nanocomposites

Abstract

Ladder-like polysilsesquioxanes (LPSQs) are characterized by a double-stranded siloxane backbone, whose chemical and structural properties depend on both the synthesis parameters and the nature of the organic side-chains. In the case of ladder-like (methacryloxypropyl) polysilsesquioxanes (LPMASQ), polymer matrices can be produced by exploiting the presence of photocurable methacrylate groups. Consequently, they can be used to prepare functional nanocomposites (NCs), either by blending with organic polymers such as polybutadiene or exploiting the inorganic fillers’ dispersion. Since the properties of LPMASQ-based NCs are strongly related to their structure, the structural changes of polymerized LPMASQ were investigated upon addition of low loadings of TiO2 nanoparticles (up to 3 wt%) by solid state nuclear magnetic resonance and X-ray diffraction. The filler addition leads to the reduction of the polymerization capacity of the LPMASQ organic side-chains. Moreover, a different organization of ladder chains has been highlighted, ascribable to the increase in fully condensed linear ladder units at the expenses of folded chains and defective structures. The methodological approach here adopted can be extended to other composite systems and may help to describe the properties at the filler-matrix interface, offering valuable hints for a better design of these materials. Graphical Abstract

SiO2@Al2O3 binary filler: A chance for enhancing the heat transport in rubber composites for tire applications

“…To further assess the binary filler surface functionalization, a 13 C CPMAS NMR spectrum was recorded on SiO 2 @Al 2 O 3 ‐TMSPM sample (Figure 4). The analysis supports the conclusions of the FTIR study, in fact all the resonances belonging to the methacryloxypropyl chain are visible 37,40 . In particular, the shift of 1 (Si‐CH 2 ‐) up to 10 ppm and the very low intensity of 8 (‐OCH 3 ) indicate an almost complete hydrolysis and condensation of the silane.…”

“…The related 29 Si CPMAS spectrum (Figure 4, right) confirms the presence of the T units onto the binary oxide particles (Q resonance centered at about −100 ppm). The TMSPM is represented by the T 2 and T 3 components at 57 and 66 ppm, respectively 37,40 . It should be mentioned that the CPMAS sequence was chosen to maximize the TMSPM signals, in fact the quantitative MAS NMR spectrum in the present case is useless due to the very low amount of T units with respect to Q.…”

“…To deepen this aspect, some NMR relaxations experiments were carried out. It is well known that the segmental motion of the long polymeric chains is usually well described by the two processes called spin–spin relaxation and spin–lattice relaxation in the rotating frame (details in the Experimental section) 39,40 . In both processes, the magnetization (peak intensity) decays with time following exponential laws ruled by two‐time constants, T 2 and T 1ρ(H) , respectively (Figure 7) The time constant values calculated for the analyzed samples from the curves in Figure S6 and Figure S7 are reported in Table S2 (Data S1).…”

“…The two experiments were tested in order to extract the time constants T 2 and T 1ρ(H) , that are correlated to different frequency ranges, and consequently their values are influenced by molecular motions on different time scales. The calculated values are commonly obtained by fitting the experimental curve ( 40 and references therein).…”

Ladder-like Poly(methacryloxypropyl) silsesquioxane-Al2O3-polybutadiene Flexible Nanocomposites with High Thermal Conductivity

“…LPSQs with methacryloxypropyl side-chains, namely ladder-like poly(methacryloxypropyl) silsesquioxanes (LPMASQ), are gels that can be easily photocured upon thermal or light-induced activation, thus providing controllable and tunable elasticity or hardness [14,15]. This feature, along with the abovementioned outstanding properties typical of SSQs, recently raised the attention of the scientific community on LPMASQ [15,16].…”