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In this work, we report for the first time on the influence of polyhedral oligomericsilsesquioxanes (POSS) on the structure and properties of liquid crystalline polyurethane (LCPU). LCPU/POSS hybrids were synthesized via a two-step method. In the first step, 4,4′-methylenephenyl diisocyanate (MDI) and polytetramethylene ether glycol (PTMG) reacted...
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... presence of the free carbonyl groups indicates that the microphase separation in the materials was incomplete. The band observed at 1650 cm −1 corresponds to the vibration of the disordered carbonyl groups that are hydrogen bonded in the soft phase, which also indicates incomplete phase separation ( Figure 3). Molecules 2019, 24, x FOR PEER REVIEW 5 of 18 polyol component. ...
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... presence of the free carbonyl groups indicates that the microphase separation in the materials was incomplete. The band observed at 1650 cm −1 corresponds to the vibration of the disordered carbonyl groups that are hydrogen bonded in the soft phase, which also indicates incomplete phase separation ( Figure 3). The intensity of the bands at 1650 cm −1 is stronger for the materials that contain POSS than for the reference materials. ...
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... Using a twostage method, firstly, a calculated amount of MDI (Methylene diphenyl diisocyanate) and PTMG (poly(tetramethylene ether)glycol) with molar mass of~650 and POSS in amounts of 0, 2, and 6 wt% were stirred (200 rpm) at a temperature of 80 • C, and then a mesogenic unit (4,4-dihydroxyhexyloxybisphenyl) was added as a chain extender in an amount of 15 wt% based on the weights of all components. The synthesis and characterization of this mesogenic unit were reported in Ref. [52]. The reaction was conducted in an inert atmosphere. ...
... The synthesis of liquid crystalline polyurethanes with POSS has already been described in [52,53], along with a detailed chemical characterization. In brief, a series of liquid crystalline polyurethanes containing two types of nanofiller were prepared. ...
... Using a two-stage method, firstly, a calculated amount of MDI (Methylene diphenyl diisocyanate) and PTMG (poly(tetramethylene ether)glycol) with molar mass of ~650 and POSS in amounts of 0, 2, and 6 wt% were stirred (200 rpm) at a temperature of 80 °C, and then a mesogenic unit (4,4-dihydroxyhexyloxybisphenyl) was added as a chain extender in an amount of 15 wt% based on the weights of all components. The synthesis and characterization of this mesogenic unit were reported in Ref. [52]. The reaction was conducted in an inert atmosphere. ...
A series of fibrous meshes based on liquid crystalline polyurethane/POSS composites were prepared. Two types of polyhedral oligomeric silsesquioxanes (POSSs) of different structures were chosen to show their influence on electrospun fibers: aromatic-substituted Trisilanolphenyl POSS (TSP-POSS) and isobutyl-substituted Trisilanolisobutyl POSS (TSI-POSS) in amounts of 2 and 6 wt%. The process parameters were selected so that the obtained materials showed the highest possible fiber integrity. Moreover, 20 wt% solutions of LCPU/POSS composites in hexafluoroisopropanol (HFIP) were found to give the best processability. The morphology of the obtained meshes showed significant dependencies between the type and amount of silsesquioxane nanoparticles and fiber morphology, as well as thermal and mechanical properties. In total, 2 wt%. POSS was found to enhance the mechanical properties of produced mesh without disrupting the fiber morphology. Higher concentrations of silsesquioxanes significantly increased the fibers’ diameters and their inhomogeneity, resulting in a lower mechanical response. A calorimetric study confirmed the existence of liquid crystalline phase formation.
... Here, the shift is closer to 50 cm -1 . Such strong shifts of bands towards lower wavenumbers due to hydrogen bonding are not common, however, they have been reported in the literature for carbonyl region in polyurethanes [19,29,30] and poly(hydroxy urethanes) [19,27,31,32]. Strongly shifted bands are associated with the presence of sterically hindered hydrogen-bonded carbonyls [31], and hydrogen bonded carbonyls in ordered state [29,30,32]. ...
... Such strong shifts of bands towards lower wavenumbers due to hydrogen bonding are not common, however, they have been reported in the literature for carbonyl region in polyurethanes [19,29,30] and poly(hydroxy urethanes) [19,27,31,32]. Strongly shifted bands are associated with the presence of sterically hindered hydrogen-bonded carbonyls [31], and hydrogen bonded carbonyls in ordered state [29,30,32]. This will be further discussed later in the text. ...
... Therefore, alternative method such as the development of composite materials is a promising approach [13,14]. ...
Herein, we report the stabilization of a nematic liquid crystal using a chiral amino acid-based polymer. For the first time, the effect of molecular weight of structurally similar polymers on the physical parameters of polymer-stabilized liquid crystals (PSLCs) is investigated. To obtain PSLCs, three pseudopeptidic bottlebrush polymers of different molecular weights are synthesized from the same monomer using a ring-opening metathesis polymerization (ROMP) reaction. The bottlebrush polymers form self-assembly networks in the LC matrix. The size of the self-assembled network is readily tunable by the systematic variation in the molecular weight of the constituent polymer. The polymer network assembly is characterized by using field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM). The ion density and diffusion coefficient of two different types of mobile ions are calculated by utilizing experimental dielectric data. The constituent polymer determines the structure of self-assembly network in PSLC and hence the dielectric, electrical, electro-optic, and optical properties. The PSLCs show significant improvement in the response time (∼21%), dielectric anisotropy (∼40%), conductivity (∼11%), current (5-fold increment at 20 V), and phase transition temperature (PTT) upon variation in the molecular weight of the doped polymer units. This simple method of tuning response time, dielectric anisotropy, conductivity, current, and PTT using polymers of different molecular weights presents several possibilities of fabricating optoelectronic devices.
... The applications have been extended to the biomedical field due to the biocompatibility of PUs [107]. Even the liquid crystalline PU (LCPU) field, when LCPU was incorporated into POSS, the LCPU/POSS hybrids could show high melting and isotropization temperatures along with the broadening phase transition effect due to the incorporation of POSS [108]. Although PUs have been used in many fields, they still have many limitations, such as poor thermal and moisture stability originating from urethane groups and low mechanical resistance due to the intrinsic hardness of the hard segments. ...
Polyhedral oligomeric silsesquioxane (POSS) has been considered as one of the most promising nanofillers in academic and industrial research due to its unique multifunctional nanostructure, easy functionalization, hybrid nature, and high processability. The progress of POSS has been extensive, particularly applications based on single- or multiple-armed POSS. In polymer hybrids, in order to enhance the properties, bifunctional POSS has been incorporated into the backbone chain of the polymer. This review summarizes recent developments in the synthesis, modification, and application of bifunctional POSS-containing composite materials. This includes amino-POSS, hydroxyl-POSS, aromatic ring-POSS, ether-POSS, and vinyl groups-POSS and their applications, exemplified by polyurethanes (PUs) and polyimides (PIs). In addition, the review highlights the enhancement of thermal, mechanical, and optical properties of the composites.
A series of liquid crystalline polyurethanes based on 4,4’-bis(hydroxyhexoxy)biphenyl moieties and modified by Trisilanolisobutyl-POSS (TRIS-POSS) was synthesized via a polyaddition reaction. ATR-FTIR confirmed introduction of POSS moieties into the macrochain. Formation of liquid crystalline phases along with higher melting and crystallization temperatures due to the addition of the POSS moieties has been observed by Differential Scanning Calorimetry (DSC) and Polarized Optic Microscopy (POM). The influence of the POSS on the improvement of thermal stability and char residue after degradation is also discussed. Influence of the POSS particles on glass transition was found to be relevant for high mesogenic unit load. Morphological investigations by Scanning Electron Microscopy showed different distribution of the POSS nanoparticles for each examined matrix and absence of POSS originated agglomerates which was also confirmed by X-ray diffraction technique. Reinforcement effect of the POSS on mechanical properties was also investigated. Mechanically induced anisotropy was hypothesized to be one of the factor responsible for improved tensile strength at high strain.
In this work, a series of hyperbranched white-emitting conjugated polymers were synthesized with polyfluorene (PF) as the branches and three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the conjugated branching point by one-pot Suzuki polycondensation, where 4,7-dithienyl-2,1,3-benzothiadiazole (DBT) as orange-light emitting unit and fluorene-containing polyhedral oligomericsilsesquioxanes (POSSs) as conjugated linking monomer were introduced into the backbones to obtain white-light emission. The influence mechanism of POSSs for hyperbranched white-emitting polymers was explored by adjusting the feeding ratios of fluorene-containing POSSs (from 1 to 20 mol%). The results indicated that the synthesized polymers still maintained the high thermal stabilities, and exhibited the improved amorphous film morphology and hydrophobicity, which were beneficial for obtaining optimized interface between the aqueous hole transport layer Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) layer and polymer light-emitting layer in device fabrication. As a consequence, all of the fabricated devices with the hyperbranched polymers as light-emitting layers realized white light-emission, and the optimized device exhibite good electroluminescent (EL) performance with Commission Internationale de l'Eclairage (CIE) coordinates at (0.32, 0.33) and maximum color rendering index (CRI) of 96. The fluorene-containing POSSs modified hyperbranched copolymers with broad full width at half maximum (>284 nm) are attractive candidates for sunlight-style white polymer light-emitting diodes.
In this work we describe the influence of nano sized materials on liquid crystalline phases in liquid crystals (LC) and liquid crystalline polymers (LCP). Methods of modification of nanoparticles (NPs) incorporated in liquid crystalline polymer matrix and liquid crystals, as well as the role of interactions between nanofiller and the polymer matrix are presented. Nanomaterials - metals, metal oxides, layered silicates, carbon nanotubes, graphene oxides, graphene nanoplatelets and polyhedral oligomeric silsesquioxanes (POSS), when incorporated into LC change their microstructure and properties. Stability of LC phase, thermal properties of nanocomposites and anisotropy effects depending on the size, shape and type of nanomaterial were discussed. Nanoparticles can increase the free volume and disturb specific interactions, such as hydrogen bonds, facilitating thus the movement of chain segments and changing the liquid crystalline transition temperatures. Application of nanomaterials may lead to new developments in medical, electro-optic and electromagnetic devices utilizing the liquid crystalline phases.
