“…The POSS inclusions also improved the tensile modulus of the TPU slightly. These results might be attributed to the formation of micro-phase separation into the TPU matrix after addition of POSS nanoparticles (Qi & Boyce, 2005; Efrat et al , 2006; Pan et al , 2019; Szefer et al , 2019; Zhao et al , 2019). Fig.…”
Section: Resultsmentioning
confidence: 99%
“…In the case of tensile modulus findings, POSS inclusions yield slightly improvement for TPU. These findings might be caused from the formation of micro-phase separation into TPU matrix after addition of POSS nanoparticles (Efrat et al, 2006;Pan et al, 2019;Szefer et al, 2019;Qi & Boyce, 2005;Zhao et al, 2019).…”
Section: Tensile Performance Of Compositesmentioning
Thermoplastic polyurethane (TPU) matrix was reinforced with polyhedral oligomeric silsesquioxane (POSS) and halloysite nanotubes (HNT), both separately and combined. Composite samples were fabricated using a melt-compounding method. Characterization of the composites obtained was performed via tensile and hardness tests, melt-flow index measurements (MFI), abrasion tests, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) to investigate the mechanical performance, flow behaviour, tribological characteristics, thermo-mechanical response and morphological properties. The greatest tensile strength value was obtained for the smallest HNT content. Further addition of HNT resulted in agglomerations for both POSS and HNT particles. The shore hardness of TPU was enhanced by filler inclusions. The TPU/POSS composites displayed significant improvement in terms of abrasion resistance compared to TPU at lower loading levels. The DMA study showed that composites containing 0.5% POSS and 1.0% HNT displayed the greatest storage modulus. The glass-transition temperature of TPU shifted to smaller values with the addition of both nanoparticles. The HNT inclusions increased the MFI value of TPU because of their large aspect ratio. Homogeneous mixing of nanoparticles in the TPU matrix was confirmed by a SEM study of the composites. Their dispersion decreased as the concentrations of POSS and HNT increased. An adjuvant effect of POSS with HNT was achieved in their hybrid composites.
“…The POSS inclusions also improved the tensile modulus of the TPU slightly. These results might be attributed to the formation of micro-phase separation into the TPU matrix after addition of POSS nanoparticles (Qi & Boyce, 2005; Efrat et al , 2006; Pan et al , 2019; Szefer et al , 2019; Zhao et al , 2019). Fig.…”
Section: Resultsmentioning
confidence: 99%
“…In the case of tensile modulus findings, POSS inclusions yield slightly improvement for TPU. These findings might be caused from the formation of micro-phase separation into TPU matrix after addition of POSS nanoparticles (Efrat et al, 2006;Pan et al, 2019;Szefer et al, 2019;Qi & Boyce, 2005;Zhao et al, 2019).…”
Section: Tensile Performance Of Compositesmentioning
Thermoplastic polyurethane (TPU) matrix was reinforced with polyhedral oligomeric silsesquioxane (POSS) and halloysite nanotubes (HNT), both separately and combined. Composite samples were fabricated using a melt-compounding method. Characterization of the composites obtained was performed via tensile and hardness tests, melt-flow index measurements (MFI), abrasion tests, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) to investigate the mechanical performance, flow behaviour, tribological characteristics, thermo-mechanical response and morphological properties. The greatest tensile strength value was obtained for the smallest HNT content. Further addition of HNT resulted in agglomerations for both POSS and HNT particles. The shore hardness of TPU was enhanced by filler inclusions. The TPU/POSS composites displayed significant improvement in terms of abrasion resistance compared to TPU at lower loading levels. The DMA study showed that composites containing 0.5% POSS and 1.0% HNT displayed the greatest storage modulus. The glass-transition temperature of TPU shifted to smaller values with the addition of both nanoparticles. The HNT inclusions increased the MFI value of TPU because of their large aspect ratio. Homogeneous mixing of nanoparticles in the TPU matrix was confirmed by a SEM study of the composites. Their dispersion decreased as the concentrations of POSS and HNT increased. An adjuvant effect of POSS with HNT was achieved in their hybrid composites.
“…This is because there is no significant difference in polymer chains containing more than 15 repeat units during optimization cycles [9,16]. Additionally, our previous reports have confirmed the effectiveness of 10-15 repeat units in constructed models [12][13][14][15]. According to Table field [17,18] were used to construct and optimize four starting single chains for each model.…”
Section: Models Construction and Optimizationmentioning
confidence: 91%
“…In their experiments, a bilayer SmC2 phase was formed when m was less than 4, while a highly ordered phase X1 was obtained when m was more than 8 [5]. In addition to the reports cited [6][7][8][9][10][11], our previous work on epoxy [12], poly(L-lactide) (PLLA) [13], and polyurethane (PU) [14,15] also indicates that there is a correlation between the regular morphology of polymers and the length of side chains. However, it is worth noting that for most polymers, changes in regularity of morphology do not always correspond to changes in side chain length.…”
Although the correlation between the regularity of micro-structures and the length of side chains has been widely reported, experiments still require precursors of polynorbornene derivatives due to the complex inter-and intra-chain interplay. This research utilizes hydrogen bonding between amide groups to design molecular models of polynorbornene derivatives (PNbs). The PNbs are abbreviated as Pm-8, where “m” indicates the amount of methylene groups as spacers in the side chain, and “8” refers to the oxyoctyl tail. The aim is to obtain a gradual variation of inter-and intra-chain interplay for further elucidation. Based on an analysis of spatial descriptors, mean square displacement (MSD), and radial distribution function (RDF) by using molecular mechanics (MM) and molecular dynamics (MD) methods, it is found that the asymmetry of side chains plays a more significant role in determining micro-structural regularity than the length. Highly asymmetric side chains are favorable for forming inter-chain hydrogen bonding, promoting interdigitation, and creating a larger scale of regularity in P8-8 and P10-8 molecules. In contrast, the relatively symmetric side chains tend to form intra-chain bonding, resulting in limited regularity within P2-8 and P4-8 molecules. Therefore, unlike regular structures that usually require symmetrical molecules, polynorbornene derivatives with asymmetric side chains have achieved highly ordered orthorhombic lattices in experiments. This study aims to offer an alternative approach to screening effective precursors of long-side chain polymers by means of semi-quantitative geometric parameters, providing a fresh perspective on the subject.
“…In more recent studies of grafted POSS systems, R. Pan et al have simulated blends of Trisilanolisobutyl POSS in polyurethane. [150] The POSS structures considered here are slightly different in that a single silicon vertex is missing from the T 8 cubic structure. Thus, the bridging oxygen atoms between silicon atoms at this vertex are hydroxyl groups, which are used for co-polymerisation with the polyurethane chains.…”
Within this thesis, I use atomistic Molecular Dynamics simulation to elucidate the thermomechanical properties of polyhedral oligomeric silsesquioxanes (POSS). These molecules have unique and interesting properties due to their nanoscale size and organic-inorganic nature. POSS species comprise a rigid silica core which is functionalised with organic moieties at the vertices. These nanoparticles exhibit a wide range of behaviours and properties due to the scope of viable functionalising groups. I largely focus here on the cubic T8 conformation, which typically ranges from 1-10 nm in diameter. For pure POSS systems, I use systematic simulation studies to characterise the sensitivity of the glass transition temperature (Tg), an important macroscopic property, to molecular structure. For POSS species functionalised with eight exible groups, I identify a key molecular feature, namely, the breathing mode, as the degree of freedom that controls the macroscopic Tg. Due to their high degree of inter-molecular entanglement, these systems exhibit very little molecular mobility. Thus, it is the molecular-level movements within the functionalising groups that underpin the systemic change from a glassy state to rubbery state. The in uence of structural morphology in tetra functionalised T8 systems are also studied. Here, I observe the adoption of richer packing arrangements and shifts in the Tg values due to alternative arrangements of the functionalising groups about the central core. I also examine the spontaneous formation of crystalline structures from amorphous starting configurations by systems of rigid POSS molecules. Due to the versatility in their structure, POSS are frequently included as a component in nanocomposite materials. Within this work, I have study POSS-polymer hybrids as both blended and grafted nanocomposites. I use hydroxyl-terminated polybutadiene (HTPB) for the polymer matrix and explain the observed changes in Tg as a product of the molecular behaviour and interactions. When grafted, POSS have a local anchoring effect on the dihedral rotational freedom available to the C-C single bonds of the HTPB backbone. Thus, I observe a significant increase in the Tg for these systems. When blended, rigid POSS hybrids exhibit significant phase separation, whereas flexible POSS species are much more dispersed within a HTPB matrix. Both systems impart less specific impact on the dihedral rotation of the HTPB matrix than is observed in the grafted systems. However, increases in Tg are consistently observed with increasing POSS concentration. Through the simulation of POSS blended with a chemically similar but sterically different matrix, I further characterise the mixing behaviours of POSS species as a function of their functionalising group. These studies provide insight into the structure-property relationship for a variety of POSS species as pure entities and nanocomposite hybrids, thus providing understanding for future programmes of synthesis or nanocomposite design, as well as necessary target properties for candidate coarse-grained models of POSS systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
