2D WAXD Research Articles

From Chitin Nanowhisker Colloidal Dispersions to Anisotropic Microfibers: Structural Evolution in Its Transformation Process as Revealed by Synchrotron Wide-Angle X-ray Diffraction Measurements.

Nanowhiskers in a colloidal dispersion are known to form chiral nematic liquid crystals (CNLC), as seen in a cellulose nanowhisker or so-called cellulose nanocrystal and chitin nanowhisker. In our related work, we clarified that once the thus-created chitin nanowhiskers with surface modified by chitosan (CTWK-CS) in CNLC phase were wet-spun, we could directly obtain anisotropic microfibers containing the highly ordered CTWK-CS. This drastic structural transformation from CNLC to anisotropic microfibers might relate to several important stages, i.e., stage (i) is the alignment of CTWK-CS initiated by a specific concentration and flow to create aggregation in the CNLC state, stage (ii) is the coagulation of CTWK-CS in CNLC to transform to microfibers, and stage (iii) is the drying of the thus-extruded microfibers to allow CTWK-CS alignment. The present work sets up the experimental systems simulating stages (i) and (iii) to reveal the orientational behavior of CTWK-CS and the structural evolution, respectively, by synchrotron 2D WAXD measurement. In stage (i), the high degree of the parallel alignments of CTWK-CS with the chain axis oriented along the flow direction of the colloidal dispersions confirms that the flow and concentration synergistically controlled CTWK-CS alignment. In contrast, for stage (iii), the poor c-axial orientation of CTWK-CS in as-spun wet microfibers gradually changed to the high degree of c-axial orientation along the fiber direction during drying process, indicating a reorientation of CTWK-CS along with dehydration. The present study declares an in situ observation of the direct wet spinning of nanowhiskers about their remarkable alignments in the sheared colloidal dispersions (stage (i)) and their random-to-high reorientation during the drying process of the as-spun wet microfiber (stage (iii)).

Structure‐Property Relationship of Polyimide Fibers with High Tensile Strength and Low Dielectric Constant by Introducing Benzimidazole and Trifluoromethyl Units

AbstractCopolyimide (co‐PI) fibers with high strength and low dielectric constant are synthesized and prepared by introducing 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl (TFMB) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA) diamines into the rigid backbones. The resultant fibers not only exhibited excellent mechanical properties with a tensile strength of 2.627 GPa and an initial modulus of 96.786 GPa, but also possessed a dielectric constant as low as 2.433 at 10 GHz. The existence of intermolecular hydrogen‐bonding interaction is confirmed by Fourier transform infrared spectroscopy, which has been considered as the leading factor responsible for the significantly improved mechanical properties of the co‐PI fibers. 2D wide‐angle X‐ray diffraction (2D WAXD) is adopted to investigate the variation on the aggregation structure of PI fibers after the incorporation of fluorine group. The fibers with more TMFB content possessed a higher orientation degree together with a larger free volume fracture due to the combined effects of enhanced flexibility and the volume effect of trifluoromethyl groups. Meanwhile, the prepared PI fibers exhibit a 5% weight loss temperature ranging from 543 to 533 °C in the nitrogen atmosphere and a glass transition temperature ranging from 334 to 317 °C, revealing high thermal stability of co‐PI fibers.

Large-Size Honeycomb-Shaped and Iris-Like Liquid Crystal Elastomer Actuators

Large-Size Honeycomb-Shaped and Iris-Like Liquid Crystal Elastomer Actuators

Long Rod-Like Liquid Crystal Containing Azobenzene and the Applications in Phase-Transition Regulation and Orientation of Nematic Liquid Crystal

Phase-transition and orientation of liquid crystal (LC) are two crucial factors for LC application. In this work, a long rod-like LC compound containing double azobenzene (M1) is successfully designed and synthesized. The combing technologies of nuclear magnetic resonance (1H NMR, 13C NMR) and Fourier transform infrared spectroscopy (FTIR) are used to identify the chemical structure of the molecule. Additionally, the polarized optical microscopy (POM), differential scanning calorimetry (DSC), and one-dimensional wide-angle X-ray diffraction (1D WAXD) experimental results show that M1 exhibits an ultrawide range of LC phases and a stable LC structure even at ultrahigh temperature, which indicates that this LC can be applied in some especial devices. Further, the compound M1 is used to tune the LC temperature range of the commercial LC 4-cyano-4′-pentylbiphenyl (5CB). A series of samples 1–7 are obtained through doping different contents of M1, which show different LC temperature ranges that are dependent on the composition ratio of M1 and 5CB. More interestingly, all resultant samples show spontaneous vertical orientation on the hydrophilic glass substrate. Meanwhile, due to the effect of azobenzene in the compound M1, a reversible transition between homeotropic to random orientation of the LC molecules is achieved when these LC cells are alternately exposed to UV irradiation and visible light, which implies that this material shows potential application in especial display and optical storage technologies.

Preparation and properties of high-performance polyimide copolymer fibers containing rigid pyrimidine and benzoxazole moieties with hydrogen bonding

The utilization of 5-amino-2-(2′-hydroxy-4′-aminophenyl)-benzoxazole (HBOA) as third monomer was beneficial for the introduction of OH-type H-bonding into polyimide (PI) matrix through the copolymerization with 2,5-bis(4-aminophenyl)pyrimidine (PRM) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). And high-performance PI fibers were successfully fabricated via the dry-jet wet spinning process. The FTIR spectra confirmed that the strong interactions of intramolecular and intermolecular H-bonding existed simultaneously in PI fibers. Moreover, the glass transition temperatures (Tg) of all fibers were within 276–318 °C, and the temperatures at 5% weight loss (T5%) ranged from 574 °C to 604 °C, revealing the remarkable thermal stability of PI fibers. The two-dimensional wide-angle X-ray diffraction (2D WAXD) results illustrated a U-shaped change in the crystallinity (from 32.1% to 12.2% until 33.4%) of PI fibers with increasing HBOA content, which was also reflected in the density variation of fibers. The two-dimensional small-angle X-ray scattering (2D SAXS) patterns demonstrated that the micro-defects in all co-PI fibers profitably decreased in comparison with those in homo-PI fibers. Furthermore, the orientation factor of fibers presented an improvement from 0.843 to 0.899 after incorporating HBOA moiety. When the molar ratio of PRM/HBOA was 7/3, the co-PI fiber exhibited optimum mechanical properties with tensile strength and modulus as high as 4.15 GPa and 125.93 GPa, respectively. Interestingly, the variation in fiber orientation was in line with the same trend as that of mechanical properties of PI fibers, indicating orientation was also a crucial factor to improve the mechanical properties. The relationship between structure and mechanical property was also investigated.

Epitaxial Crystallization of Poly(ε-caprolactone) on Reduced Graphene Oxide at a Low Shear Rate by In Situ SAXS/WAXD Methods.

The interfacial interaction between polymers and reinforcements has a positive effect on the properties of polymer nanocomposites, and a further study on the evolution of this interfacial interaction under a shear field is conducive to reasonable regulation of the properties of polymer nanocomposites. For this purpose, epitaxial crystallization of poly(ε-caprolactone) (PCL) on reduced graphene oxide (RGO) is investigated by shearing at the shear rate of 3 s–1 by in situ synchrotron radiation. In situ two-dimensional small-angle X-ray scattering (2D SAXS) results suggest that the imposed shear field promotes the orientation of the polymer chains, resulting in the formation of a large periodic structure of PCL on the RGO surface. In addition, higher shear temperatures facilitate the conformational adjustment of the PCL molecular chain on RGO at the shear rate of 3 s–1, resulting in the formation of thicker lamellae. In situ two-dimensional wide-angle X-ray diffraction (2D WAXD) results show that shear enhances the crystallinity of the PCL/RGO nanocomposite and promotes the oriented growth of epitaxial and bulk crystals. The current findings can improve the understanding of the structural evolution behavior of PCL/RGO nanocomposites after shear and especially enhance dramatically our understanding of the underlying mechanism of influence of shear on interfacial epitaxial crystallization in polymer/graphene nanocomposite systems.

Structure and Properties of Aromatic Polyimide Fibers Fabricated by a Novel “Reaction-Spinning” Method

In this work, two sets of high performance polyimide (PI) fibers fabricated by a more environmentally-friendly and highly efficient “reaction-spinning” method were firstly reported. The relationship between the spinning rate, chemical structure and the imidization degree of the PI precursor fibers were investigated, and the results indicated a moderate low spinning speed and relatively flexible molecular chains are both favorable for the partial imidization reaction in the spinning process. 2D WAXD results demonstrate that the rigid PDA-based PI fibers possess a higher alignment of polymer chains along the fiber axis during the spinning compared to the flexible ODA-based PIs, resulting in enhanced mechanical properties, with the tensile strength of 1.2-2.8 GPa and modulus of 53.6-111.2 GPa, respectively. Meanwhile, ODA sets of PI fibers exhibit a higher loop strength and knot strength than the commercial Aramid and PBO fibers. The process used in this study has a significant potential for realizing industrial level production of high strength and high modulus PI fibers. Open image in new window

The Influence of Space Restriction on the Mechanical Properties of Isotactic Polypropylene/Reduced Graphene Oxide Nanocomposite Injection Bars

Isotactic polypropylene (iPP)/reduced graphene oxide (RGO) nanocomposite bars were prepared by injection molding and the effects of RGO on the iPP matrix were investigated via differential scanning calorimetry, two dimensional wide angle X-ray diffraction (2D WAXD) and small angle X-ray scattering (2D SAXS) techniques. It is demonstrated that RGO is an effective nucleation agent for iPP and the incorporation of RGO can enhance the degree of orientation of iPP crystals at flow direction. Furthermore, the orientation of iPP chains at flow direction intensifies with the increase of RGO contents, which can be attributed to that RGO obstructed the motion of orientated polymer chains. Although the enhancement effect is weaker than that of High density polyethylene (HDPE)/RGO nanocomposites with epitaxial crystallization, the mechanical properties of iPP/RGO nanocomposites can also be improved apparently.

High Efficiency Luminescent Liquid Crystalline Polymers Based on Aggregation-Induced Emission and “Jacketing” Effect: Design, Synthesis, Photophysical Property, and Phase Structure

A series of high efficiency luminescent liquid crystalline polymers (LLCPs) based on aggregation-induced emission (AIE) and the “Jacketing” effect, namely, poly{2,5-bis{[2-(4-oxytetraphenylethylene)-n-alkyl]oxycarbonyl}styrene} (denoted as Pm, m = 2, 4, 6, 8, 10, 12), were successfully designed and synthesized via introducing tetraphenylethylene to the side group with different length spacers. Because of the AIE effect, the resultant LLCPs are completely free of aggregation caused quenching. The photophysical properties and phase behavior were studied via various techniques such as UV–vis absorption spectra, photoluminescence spectra (PL), polarized light microscopy (PLM), differential scanning calorimetry (DSC), and variable temperature one-dimensional wide-angle X-ray diffraction (1D WAXD). The results revealed that the resultant monomers showed typical AIE behavior and the polymers exhibited aggregation enhanced emission (AEE) behavior. Moreover, due to the “Jacketing” effect, the polymers showed high ...

Synthesis of organosoluble copolyimide and preparation of fibers by dry-spinning process on a large scale

An organosoluble copolyimide (co-PI) was synthesized from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 1,4-bis-(4-aimino-2-triflupromethyl-phenoxy)-benzene ( p-6FAPB), and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) via the one-step polymerization using N-methyl-2-pyrrolidone (NMP) as the solvent, and high-performance co-PI fibers were directly prepared by the dry-spinning process on a large scale. Scanning electron microscopic images show that all formulations of as-spun fibers exhibit elliptical cross sections as well as dense morphologies. The structural evolution of the co-PI fiber induced by the high rolling speed and post-heat-drawing treatment was studied by means of thermogravimetric analysis, dynamic thermomechanical analysis, and two-dimensional wide-angle X-ray diffraction (2D WAXD). With increasing rolling speeds, glass transition temperatures ( Tgs) and thermal stabilities of as-spun fibers slightly decrease, which may be resulted from the disentanglement of entangled molecular chains under the large deformation and high-temperature heating atmosphere in the spinning column. 2D WAXD data indicate that both increasing rolling speeds and post-heat-drawing treatment are beneficial for getting a highly ordered structure along the meridian direction of the fibers. The fibers treated at 430°C exhibit outstanding mechanical properties, and the tensile strength and modulus reach 1.44 GPa and 48.69 GPa, respectively, at a drawing ratio of 2.8.

2D Organic Superlattice Promoted via Combined Action of π-π Stacking and Dipole-Dipole Interaction in Discotic Liquid Crystals.

A series of discotic liquid crystals based on hexapentyloxytriphenylene (HAT5) have been investigated where one out of the six ether side chains of a triphenylene core was replaced by an ester side chain and named for 5a-5h. During the process of studying these compounds, the characteristic straight line defect of ordered columnar structure was identified by polarizing optical microscopy (POM) and liquid crystal state over a wide temperature range was obtained by differential scanning calorimetry (DSC). Basic phase structure and molecular arrangement were assigned by one-dimensional wide-angle X-ray diffraction (1D WAXD), small-angle X-ray scattering (SAXS), two-dimensional wide-angle X-ray diffraction (2D WAXD), and transmission electron microscope (TEM). Combined with sharp and regular dots in 2D WAXD patterns and characteristic peaks at small angle in SAXS pattern which indicated the existence of superlattice, we proved that 2D superlattice formed from self-assembly of discotic molecules with a polar group via π-π stacking and dipole-dipole interaction. In order to verify the effect of orientation on charge carrier mobility, their electron and hole mobilities were measured by time-of-flight (TOF) device, among which the charge carrier mobility could achieve almost twice as that of HAT5. The formation of superlattice no doubt improved their electronic properties and made them more attractive in organic electronics.

Effect of thermomechanical post-processing on chain orientation and crystallinity of electrospun P(VDF-TrFE) nanofibers

The electromechanical coupling behavior in piezoelectric polymers strongly depends on their morphology. The electromechanical coupling is defined as the conversion between electrical energy and mechanical energy in piezoelectric materials. Geometry (nanofibers, films, etc.) as well as fabrication methods, and post-processing affect crystallinity, orientation, and size of the crystallites, and alignment of the chains in semicrystalline structure of these polymers. This study reports on the effects of thermal annealing and stretching (drawing) as two post-processing treatments on mechanical and piezoelectric properties of P(VDF-TrFE) (poly[(vinylidenefluoride)-co-trifluoroethylene]) nanofibers produced by electrospinning process. Tensile test, X-ray diffraction and 2D WAXD, DSC, polarized FTIR, and piezoresponse force microscopy (PFM) were utilized to investigate the post-processing – morphology – property relationship in these nanofibers. The results show that annealing and stretching (drawing) improved elastic modulus and strength of the nanofibers by more than two times, while piezo response of single fiber increased by ∼1.7 times, which overall resulted in ∼5.5 times enhancement in electromechanical coupling factor. Comparison between two post-processing treatments revealed that annealing had more effect on improvement of thermomechanical coupling factor as compared to drawing.

Influence of the spacer on the phase behaviors of side-chain liquid crystalline copolymers based on triphenylene discotic mesogen unit

Based on two analogous triphenylene liquid crystalline monomers (MTS and MT6S), a novel series of binary copolymers poly{[3,6,7,10,11-pentakis(hexyloxy)-2-oxytriphenylene]methacrylate-co-6-[3,6,7,10,11-pentakis(hexyloxy)-2-oxytriphenylene]hexyl methacrylate} (poly(MTSx-co-MT6Sy)) were prepared by free radical polymerization using AIBN as initiator. The random nature of the copolymers was expected on the basis of the assumed similar reactivities due to the analogous triphenylene monomers. The phase behaviors of copolymers were studied by DSC, POM and 1D WAXD. The results showed that the content of PMT6S has a significant effect on the liquid crystalline (LC) phase behaviors and phase structures of copolymers. The comparison between PMTS and PMT6S indicates that the content of the spacer was crucial to determine the LC structures. The PMTS formed a stable columnar nematic phase (ΦN) and the PMT6S exhibited a stable hexagonal columnar phase (ΦH). After copolymerization, the glass transition temperature and the phase transition temperature of the copolymers from the LC phase to isotropic phase both decreased with the molar fraction of PMT6S in the feed. The samples whose molar content of PMT6S was below 75% formed stable ΦN, similar to the property of PMTS. The samples whose molar content of PMT6S was above 80% presented the symmetry ΦH, similar to the property of PMT6S. Through copolymerization, one can better understand the interrelation of microstructures and how Tp mesogenic orders constitute the key basis for various applications.

Preparation of high-performance polyimide fibers containing benzimidazole and benzoxazole units

A series of aromatic copolyimide (co-PI) fibers containing benzimidazole and benzoxazole were prepared by introducing 5-amino-2-(4-aminobenzene)benzoxazole (BOA) and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) into the rigid 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)/p-phenylenediamine (p-PDA) backbone via a typical two-step wet-spinning method. The incorporated BOA and BIA moieties in the polymer chains resulted in significant changes on the comprehensive performances of the resulting PI fibers. The optimum tensile strength was 2.26 GPa with the BIA/BOA molar ratio of 3/1, whereas the optimum initial modulus was 145.0 GPa with the BIA/BOA molar ratio of 1/3. The drastically improved mechanical properties were originated from the hydrogen-bonding intermolecular interactions by BIA moieties and high molecular orientation by BOA moieties. FT-IR results confirmed the presence of hydrogen-bonding interaction in the fibers with high imidization degree. Two-dimensional wide-angle X-ray diffraction (2D WAXD) indicated the existence of highly oriented structures along the fiber axial direction, while this feature varied with different diamine ratios. SEM observations showed that the fibers were obtained with homogeneous and uniform structures at various diamine ratios. Meanwhile, the co-PI fibers exhibited excellent thermal properties with 5 % weight loss temperature ranging from 563 to 570 °C in nitrogen and glass transition temperature ranging from 308 to 321 °C.

Synthesis and liquid crystalline behavior of side chain liquid crystalline polymers containing triphenylene discotic mesogens with different length flexible spacers

A series of side chain liquid crystalline polymers (SCLCPs) containing triphenylene (Tp) units in the side chains, denoted as PMTS (without spacer) and PMTnS (n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains), with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/13C-NMR, and the phase behaviors were examined by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (1D and 2D WAXD). The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3S, PMT4S and PMT6S, they formed the symmetry hexagonal columnar (ΦH) phase owing to the decoupling effect. All of these indicated that the “decoupling effect” or “coupling effect” depended on the length of spacers, leading to the different LC phase formation mechanism.

Combined main-chain/side-chain ionic liquid crystalline polymer based on ‘jacketing’ effect: Design, synthesis, supra-molecular self-assembly and photophysical properties

Reasonably fabricating ordered structures of ionic polymers is very important for the development of novel func- tional materials. By combining the ions and liquid cry stalline polymer, we successfully designed and synthesized a series of novel combined main-chain/side-chain ionic liquid crystalline polymer (MCSC-ILCPs) containing imidazolium groups and different counter-anions, poly (2,5-bis{(6-(4-butoxy-4!-imidazolium biphenyl)hexyl)oxycarbonyl}styrene salts) poly(BImBHCS-X) with the following types of counter-anions (Br, BF4, PF6 and TFSI). Combined technologies con- firmed the chemical structures of the monomers and polymers with imidazolium cation and different counter-anions. Dif- ferential scanning calorimetry (DSC), polarized light microscopy (PLM) and one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD) results illustrated that the LC structures and the transitions of ordered structures depended on the nature of the counter-anion employed. The polymers with Br and BF4 counter-anions exhibited smectic A (SmA) LC behavior below the isotropic temperature. The another one, poly(BImBHCS-TFSI) with the large volume of the TFSI anion destroyed the packing of the LC ordered structure resulting in an amorphous structure. The photophysical properties of the polymers prepared can be adjusted by tuning the ionic interaction of the polymers by switching the counter-anion.

Manipulating ordered structure of ionic liquid crystalline polymers through tuning the alkyl spacer length

The fabrication of ordered structure is very important for the applications of ionic liquid crystalline polymers (ILCPs) or polymerized (ionic liquid crystal) (PILC). In this paper, we reported a facile approach to manipulate the ordered structure of ILCPs through adjusting the length of alkyl spacer. We designed and synthesized a series of ILCPs contained imidazolium, poly(2,5-bis{[m-(4-butoxy-4′-imidazolium phenyl) m-alkyl] oxy carbonyl} styrene bis (fluoroborate) salts) (denoted as P4-m−BF4, m represents the number of carbon in the alkyl spacers and m = 2, 4, 6, 10) via radical polymerization. Combined differential scanning calorimetry (DSC), polarized light microscopy (PLM), X-ray scattering, and two-dimensional wide-angle X-ray diffraction (2D WAXD), we found that the ordered structure of this ILCPs can transfer from smectic A phase (SmA) to hexagonal columnar (ΦH) phase with the increase of spacer. Furthermore, these results were confirmed by reconstructed relative electron density map using fast fourier transform algorithm (FFT). The result revealed that the increase of alkyl spacer would affect the interaction between ions and side chain, and induce the packing of the side chains. It was evident that the alkyl spacer played an important role in the constructing of ordered structure and offered a new method to fabricate different ordered structure of ILCPs.

Structure and Properties of Regenerated Cellulose Filaments Prepared from Cellulose Carbamate–NaOH/ZnO Aqueous Solution

In this work, regenerated cellulose (RC) filaments were successfully spun from cellulose carbamate in a NaOH/ZnO aqueous solution on a pilot scale. The structure and properties of the RC filaments were characterized using SEM, FT-IR, elemental analysis, 13C NMR, XRD, 2D WAXD, tensile testing, and dye testing. The nitrogen-free and sulfur-free RC filaments exhibited a bright surface and circular cross section. The filaments demonstrated a typical cellulose II crystal structure and a relatively high degree of orientation. Improved tenacity and structure were obtained in the RC fibers due to improved post-processing spinning steps and an increased drawing ratio. The tenacity of the fibers was determined in the range of 1.69–2.36 cN/dtex, which was comparable with that of commercial viscose rayon. Furthermore, the RC filaments showed improved dye properties compared with viscose rayon. The described carbamate pathway provided a simple and environmentally friendly method, offering an alternate to the environmental drawbacks of the viscose process.

Hydrogen‐Bonding Interactions and Molecular Packing in Polyimide Fibers Containing Benzimidazole Units

Rigid‐rod polyimides (PI) containing benzimidazole moieties were synthesized and spun into fibers by a wet‐spinning method. The resultant fibers exhibited an optimum tensile strength of 2.15 GPa and an initial modulus of 105 GPa with a low elongation of 2.2%. The PI fibers consisting of various ratios of 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl (TFMB) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA) were investigated by Fourier transform infrared spectroscopy and two‐dimensional wide angle X‐ray diffraction (2D WAXD). Direct evidence of hydrogen‐bonding involving the NH groups of BIA and the imide carbonyls is presented. Qualitative and quantitative information of this molecular interaction was obtained and discussed. This has been considered as a main factor responsible for the significantly improved mechanical properties of the PI fibers. 2D WAXD and molecular mechanics modeling were used to simulate the structure of the aromatic PI fibers. As a result, the addition of BIA in the main chains is to increase the regularity of the molecule packing, which plays an important role in the enhanced strength of the PI fibers with more BIA loadings.

Synthesis and Phase Structures of Dendronized Polymers with Dendritic Azobenzene Side Groups Based on Mesogen-Jacketed Liquid Crystalline Polymers

The first- and second-generation dendronized polymers, poly (2, 5-bis {[3, 5-di (4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (PG1) and poly (2, 5-bis {3, 5-di [3, 5-di (4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (PG2), were successfully synthesized, and their phase structures were investigated by differential scanning calorimetry (DSC), polarized light microscopy (PLM), and one-dimensional wide-angle X-ray diffraction (1D WAXD). The results show that the liquid crystalline (LC) phase structures of the dendronized polymers containing dendritic azobenzene side groups depend strongly on the molecular weights (MWs) and the generation of dendritic azobenzene side groups. Compared the low MWs PG2 with the low MWs PG1, the degree of order in LC phase increased with increasing the generation of dendritic azobenzene side groups.