Compendium of the most significant studies with reference to properties, intake, effects.

Boldyrev K , Chernyak A , Meshkov I , Muzafarov A , Tatarinova E , Vasil'ev S . The self-diffusion of polymethylsilsesquioxane (PMSSO) dendrimers in diluted solutions and melts. Soft Matter. 2020 Nov 4;16(42):9712-9725. doi: 10.1039/d0sm01183e. 

Abstract. Recently developed non-functional derivatives of polymethylsilsesquioxane (PMSSO) dendrimers of the first to fifth generation were characterized by 1H, 13C and 29Si NMR spectroscopy. The self-diffusion and NMR relaxation of PMSSO dendrimers in dilute solutions of toluene and melts were investigated in a wide temperature range (-50-80 °C). The hydrodynamic radii of dendrimers were determined from the self-diffusion coefficients measured in diluted solutions according to the Stokes-Einstein equation. The hydrodynamic radius of PMSSO dendrimers as a function of molecular mass follows a power law with the scaling exponent of 0.32 ± 0.02 in the investigated temperature range. The temperature dependences of the self-diffusion coefficients of dendrimers were described by the Arrhenius-type equation. The activation energies of self-diffusion of dendrimers in diluted toluene solutions are identical for different generations while the dependence of activation energy for dendrimers in melts shows a maximum for the third generation (G3) dendrimer. Taking into account the absence of specific interactions in PMSSO dendrimer melts the observed behavior was ascribed to the manifestation of interpenetration of dendrimer molecules. For low generations (G1 and G2) the short length of the branches does not considerably affect the translational diffusion while for higher generations (G4 and G5) the densification of the structure prevents significant interpenetration.

Kucuk I, Edirisinghe M. Microfluidic preparation of polymer nanospheres. J Nanopart Res. 2014;16(12):2626. doi: 10.1007/s11051-014-2626-5. 

Abstract. In this work, solid polymer nanospheres with their surface tailored for drug adhesion were prepared using a V-shaped microfluidic junction. The biocompatible polymer solutions were infused using two channels of the microfluidic junction which was also simultaneously fed with a volatile liquid, perfluorohexane using the other channel. The mechanism by which the nanospheres are generated is explained using high speed camera imaging. The polymer concentration (5-50 wt%) and flow rates of the feeds (50-300 µl min-1) were important parameters in controlling the nanosphere diameter. The diameter of the polymer nanospheres was found to be in the range of 80-920 nm with a polydispersity index of 11-19 %. The interior structure and surfaces of the nanospheres prepared were studied using advanced microscopy and showed the presence of fine pores and cracks on surface which can be used as drug entrapment locations.

Maleki H, Whitmore L, Hüsing N. Novel multifunctional polymethylsilsesquioxane-silk fibroin aerogel hybrids for environmental and thermal insulation applications. J Mater Chem A Mater. 2018 Jul 14;6(26):12598-12612. doi: 10.1039/c8ta02821d. 

Abstract. The development of aerogels with improved mechanical properties, to expand their utility in high-performance applications, is still a big challenge. Besides fossil-fuel based polymers that have been extensively utilized as platforms to enhance the mechanical strength of silsesquioxane and silica-based aerogels, using green biopolymers from various sustainable renewable resources are currently drawing significant attention. In this work, we process silk fibroin (SF) proteins, extracted from silkworm cocoons, with organically substituted alkoxysilanes in an entirely aqueous based solution via a successive sol-gel approach, and show for the first time that it is possible to produce homogeneous interpenetrated (IPN) polymethylsilsesquioxane (PMSQ)-SF hybrid aerogel monoliths with significantly improved mechanical properties. Emphasis is given to an improvement of the molecular interaction of the two components (SF biopolymer and PMSQ) using a silane coupling agent and to the design of pore structure. We succeeded in developing a novel class of compressible, light-weight, and hierarchically organized meso-macroporous PMSQ-SF IPN hybrid aerogels by carefully controlling the sol-gel parameters at a molecular level. Typically, these aerogels have a compressive strength (δ max) of up to 14 MPa, together with high flexibility in both compression and bending, compressibility up to 80% strain with very low bulk density (ρ b) of 0.08-0.23 g cm-3. By considering these promising properties, the superhydrophobic/oleophilic PMSQ-SF aerogel hybrids exhibited a high competency for selective absorption of a variety of organic pollutants (absorption capacities ∼500-2600 g g-1 %) from water and acted as a high-performance filter for continuous water/oil separation. Moreover, they have demonstrated impressive thermal insulation performance (λ = 0.032-0.044 W m-1 K-1) with excellent fire retardancy and self-extinguishing capabilities. Therefore, the PMSQ-SF aerogel hybrids would be a new class of open porous material and are expected to further extend the practical applications of this class of porous compounds.

Li T, Du A, Zhang T, Ding W, Liu M, Shen J, Zhang Z, Zhou B. Efficient preparation of crack-free, low-density and transparent polymethylsilsesquioxane aerogels via ambient pressure drying and surface modification. RSC Adv. 2018 May 16;8(32):17967-17975. doi: 10.1039/c8ra03061h. 

Abstract. Polymethylsilsesquioxane (PMSQ) aerogels have gained considerable attention due to their high transparency, good mechanical properties and low thermal conductivity. However, low-density PMSQ aerogels are difficult to obtain by ambient pressure drying due to irreversible shrinkage. Inspired by previous research, we speculate that reducing surface silanol groups could reduce irreversible shrinkage along with the skeleton-strengthening effect. In addition, extending the ageing process is expected to lead to increased density. Thus, in this paper, we applied a mature technique to modify the surfaces of PMSQ gels with terminal silane groups to reduce hydrophilic surface silanol groups without strengthening the skeletons. This surface modification process greatly reduced irreversible shrinkage and allowed the PMSQ gels to return to their original sizes, in accompany with the decrease of silanol group (NMR results as the direct evidence). This method exhibits extremely high efficiency in the preparation of crack-free, low-density and transparent PMSQ aerogels. The PMSQ aerogels dried at ambient pressure had a low density of 48 mg cm-3, low thermal conductivity (21.1 mW m-1 K-1), high transparency (81.3% at 550 nm), super-hydrophobicity (contact angle of 155°) and excellent mechanical properties. The proposed method will be useful for the industrial production of transparent insulating materials and has potential applications in space exploration.This journal is © The Royal Society of Chemistry.

Fouad E, Baatti A, Ben Hamou K, Kaddami H, Souli M, Imad A. Investigation on the Thermoforming of Pmsq-Hdpe for the Manufacture of a NACA Profile of Small Dimensions. Polymers (Basel). 2021 May 17;13(10):1622. doi: 10.3390/polym13101622.

Abstract. Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation industry, both for military and civilian applications. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum and carbon fiber. In this regard, a new family of high-density polyethylene (HDPE) nanocomposites reinforced with polymethylsilsesquioxane nanoparticles (PMSQ), with mechanical performances significantly superior to those of pure HPDE, has been prepared by a fusion-combination process. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. Then, the Lagrangian formulation and the membrane theory assumption were used in the explicit implementation of the dynamic finite element formulation. For the forming phase, we considered the thermodynamic approach to express the external work in terms of closed volume. In terms of von Mises stress distribution and thickness in the blade, the results indicate that HDPE-PMSQ behaves like virgin HDPE. Furthermore, its materials, for all intents and purposes, require the same amount of energy to form as HDPE.

Hayase, G., Kanamori, K., Abe, K., Yano, H., Maeno, A., Kaji, H., & Nakanishi, K. (2014). Polymethylsilsesquioxane–cellulose nanofiber biocomposite aerogels with high thermal insulation, bendability, and superhydrophobicity. ACS applied materials & interfaces, 6(12), 9466-9471.

Abstract. Polymethylsilsesquioxane–cellulose nanofiber (PMSQ-CNF) composite aerogels have been prepared through sol-gel in a solvent containing a small amount of CNFs as suspension. Since these composite aerogels do not show excessive aggregation of PMSQ and CNF, the original PMSQ networks are not disturbed. Composite aerogels with low density (0.020 g cm–3 at lowest), low thermal conductivity (15 mW m–1 K–1), visible light translucency, bending flexibility, and superhydrophobicity thus have been successfully obtained. In particular, the lowest density and bending flexibility have been achieved with the aid of the physical supporting effect of CNFs, and the lowest thermal conductivity is comparable with the original PMSQ aerogels and standard silica aerogels. The PMSQ-CNF composite aerogels would be a candidate to practical high-performance thermal insulating materials.