Showing papers in "Liquid Crystals in 2010"
TL;DR: In this paper, the synthesis and characterisation of three sets of non-symmetric liquid crystal dimers consisting of a cholesteryl-based unit and either 4-methoxybiphenyl, 4-cyanobiphensyl or (S)-2-methylbutyl 4′oxybipphenyl-4-carboxylate are described.
Abstract: The synthesis and characterisation of three sets of non-symmetric liquid crystal dimers consisting of a cholesteryl-based unit and either 4-methoxybiphenyl, 4-cyanobiphenyl or (S)-2-methylbutyl 4′oxybiphenyl-4-carboxylate are described. The transitional properties of these non-symmetric dimers are compared to those of the corresponding parent symmetric dimers. The symmetric dimers exhibit only chiral nematic or nematic phase behaviour. By contrast, members of the non-symmetric dimer series containing either 4-cyanobiphenyl or (S)-2-methylbutyl 4′-oxybiphenyl-4-carboxylate groups exhibit smectic behaviour. The former series show an interdigitated smectic A phase while for the latter the structure of the smectic A phase depends on the length of the flexible spacer. Specifically, for short spacer lengths a monolayer arrangement is seen while for long spacers an intercalated smectic A phase is formed. For an intermediate spacer length, the small-angle X-ray scattering pattern for the intercalated smectic A ph...
151 citations
TL;DR: In this paper, the authors investigated disodium cromoglycate using deuteron magnetic resonance spectroscopy and found that the quadrupolar splitting of the D2O spectrum increased with decreasing temperature and that the addition of salt to the solution increased the temperature stability of the nematic phase.
Abstract: Almost 30 years ago, when the study of chromonic liquid crystals was in its infancy, Alfred Saupe and L.J. Yu investigated disodium cromoglycate using deuteron magnetic resonance spectroscopy. Among their findings were that the quadrupolar splitting of the D2O spectrum increased with decreasing temperature and that the addition of salt to the solution increased the temperature stability of the nematic phase. A good deal of research on chromonic liquid crystals has been reported since that time, and therefore a lot more is known. However, it is also interesting that some of the questions from that time remain unanswered.
74 citations
TL;DR: In this article, a new cell structure with a protrusion shape of electrode and a driving scheme using two transistors to reduce operating voltage and enhance light efficiency was proposed for liquid crystal displays based on the Kerr effect.
Abstract: Liquid crystal displays based on the Kerr effect are emerging because of their attractive features, such as symmetric viewing angle, no need for alignment layer, and sub-millisecond response time. However, high operating voltage and low optical efficiency remain as challenges to be overcome. Here, we propose a new cell structure with a protrusion shape of electrode and a driving scheme using two transistors to reduce operating voltage and enhance light efficiency. Confirming simulation results are obtained.
67 citations
TL;DR: In this article, a review of linear and quadratic electromechanical effects of liquid crystals is presented, and an overview of the electrostriction effects in fluid, polymeric and rubber-like liquid-crystalline systems is given.
Abstract: Linear and quadratic electromechanical effects of liquid crystals are reviewed. Among the linear effects the piezoelectric and flexoelectric effects and their analogues in low molecular weight fluid, nematic, smectic and columnar liquid crystals, in polymeric and elastomer liquid crystals, are discussed and compared with the piezoelectricity of conventional solid piezoelectrics. As the most important quadratic electromechanical effect, an overview is given of the electrostriction effects in fluid, polymeric and rubber-like liquid-crystalline systems. These topics are rarely discussed in the liquid crystal literature, although they are becoming increasingly important for future energy conversion and micro-energy-generating devices.
56 citations
TL;DR: In 1970, two seemingly unrelated reports about nematic liquid crystals appeared in the scientific literature: at Kent State University, Adrian de Vries reported local smectic order in a nematic that he termed cybotactic, and at IBM, Marvin Freiser showed the possibility of a lower symmetry nematic named biaxial as mentioned in this paper.
Abstract: In 1970, two seemingly unrelated reports about nematic liquid crystals appeared in the scientific literature: at Kent State University, Adrian de Vries reported local smectic order in a nematic that he termed cybotactic, and at IBM, Marvin Freiser showed the possibility of a lower symmetry nematic that he named biaxial. These two discoveries are connected through consideration of the origins of spontaneous symmetry breaking, in particular, how broken symmetry within transient clusters permeating a nominally uniaxial nematic may lead to a biaxial nematic.
55 citations
TL;DR: In this article, the phase of a liquid crystal changing from a nematic phase to a cholesteric mesophase is achieved by adding different ratios of chiral dopants S811.
Abstract: The phase of a liquid crystal (LC) changing from a nematic phase to a cholesteric (Ch) mesophase is achieved by adding different ratios of chiral dopants S811. By studying the transmission spectrum, we are able to measure the helical pitch in cholesteric phase. The pitch in the mixtures of nematic E7 and chiral dopants S811 as a function of the concentration of the dopant and temperature is investigated. The sensitivity of the selective reflection notch of the cholesteric phase to the thermal tuning depends strongly on the ratios of the chiral dopants. It reveals that the influence of temperature is more profound for those cholesteric liquid crystals (CLCs) which exhibit smectic A (SmA) at lower temperatures. When fitted using Keating's formula, the helical pitch calculated from our experimental results lies on the predicted curve. Optimised ratios of the mixture CLCs for the optimised reflection band with the specified wavelength ranging from 467 nm to 2123 nm are suggested.
54 citations
TL;DR: In this article, ordered micellar and inverse mousellar lyotropic liquid-crystalline phases that can be formed by amphiphilic molecules such as lipids and surfactants are reviewed.
Abstract: In this article we review the ordered micellar and inverse micellar lyotropic liquid-crystalline phases that can be formed by amphiphilic molecules such as lipids and surfactants. We focus first on the self-assembly of amphiphiles into aggregates, and then consider the interfacial curvature and the role of curvature elasticity and packing constraints in determining the allowed structures. We then review the range of ordered micellar and inverse micellar phases that have so far been observed in a variety of surfactant and lipid systems. Finally, we describe certain characteristic properties, such as the epitaxy between phases, and the self-diffusion and electrical conductivity within such ordered micellar phases.
54 citations
TL;DR: In this paper, anisotropic ion transport and organized reaction media/solvents are used for a number of applications such as ion transport, and as organised reaction media and solvents.
Abstract: Thermotropic ionic liquid crystals (LCs) are useful for a number of applications such as anisotropic ion transport and as organised reaction media/solvents because of their ordered fluid properties...
54 citations
TL;DR: In this paper, the influence of the length of the chain length of crosslinkers on the electrooptic properties of PDLC films was studied and it was proved that adjusting the chain lengths of the crosslinking agents and the LC content can produce PDLC film with good electro-optic property with a lower LC content.
Abstract: Polymer-dispersed liquid crystal (PDLC) films were prepared by photochemical polymerisation from an ultraviolet-curable monomer/crosslinking agent/initiator/liquid crystal (LC) mixture. The influences of the chain length of crosslinking agents on the PDLC system have been studied. The microstructures of the PDLC films were strongly influenced by the chain length of the crosslinker, which in turn influences the electro-optic properties of PDLC films. It is proved that adjusting the chain length of the crosslinking agents and the LC content can produce PDLC films that have good electro-optic properties with a lower LC content.
49 citations
TL;DR: A series of new calamitic liquid crystals, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, comprising a benzothiazole core, terminal methoxy group and a Schiff base linkage were synthesized and characterised.
Abstract: A series of new calamitic liquid crystals, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, comprising a benzothiazole core, terminal methoxy group and a Schiff base linkage were synthesised and characterised. This series comprises 12 members wherein members differ by the length of the alkanoyloxy chain (C n-1H2n-1COO-, where n = 2–8, 10, 12, 14, 16, 18). Their mesomorphic properties were studied by using differential scanning calorimetry, optical polarising microscopy and powder X-ray diffraction techniques. The short chain derivatives (n = 2 and 3) were non-mesogenic compounds, while an enantiotropic nematic phase was present throughout the remaining members of the series. The smectic C phase emerged from the decanoyloxy derivative onwards.
49 citations
TL;DR: In this article, the authors presented the characterisation and dielectric relaxation spectroscopy of a ferroelectric liquid crystal (FLC), namely KCFLC 7S, and observed that the studied FLC material possesses the tendency of homeotropic alignment on glass substrates coated with indium tin oxide.
Abstract: We present the characterisation and dielectric relaxation spectroscopy of a ferroelectric liquid crystal (FLC), namely KCFLC 7S. It was observed that the studied FLC material possesses the tendency of homeotropic alignment on glass substrates coated with indium tin oxide. A low frequency dielectric mode, along with the Goldstone mode, was observed in the SmC* phase of the FLC material. The low frequency mode became more dominant on doping gold nanoparticles into the FLC material. The occurrence of the low frequency mode was attributed to the ionisation–recombination-assisted diffusion of slow ions present in the FLC material. The behaviour of the relaxation frequency of the low frequency mode with applied dc bias and temperature was also demonstrated.
TL;DR: In this article, the authors characterize the resistance of diffractive waveplates to optical radiation, the effects of temperature and deformations, and the boundary effects in the manufacturing process make it necessary to use substrates larger than the desired aperture of the DW.
Abstract: The development history of polarization gratings (PGs), with origins in holography and Bragg gratings, accentuated and
reinforced their perception as gratings. We highlight their nature as waveplates - diffractive waveplates (DWs) - and
stress their family connection to vector vortex waveplates. This approach provides a straightforward understanding of
the unusual properties of PGs, such as nearly 100% diffraction in thin material layers, the presence of only one
diffraction order for a circularly polarized beam, wide diffraction bandwidth and the possibility of achromatic behavior.
With technology being ripe for applications such as beam steering, and optical switching, we characterize the resistance
of DWs to optical radiation, the effects of temperature and deformations. We also show that the boundary effects in the
manufacturing process make it necessary to use substrates larger than the desired aperture of the DW. The multicomponent
systems are discussed for developing normally transmissive switchable imaging systems, beam scanning, and
achromatic diffraction.
TL;DR: In this paper, board-like goethite (α-FeOOH) particles with short-range repulsive interaction form a versatile colloidal model system, showing a nematic, smectic A and columnar phase.
Abstract: Dispersions of board-like goethite (α-FeOOH) particles with short-range repulsive interaction form a versatile colloidal model system, showing a nematic, smectic A and columnar phase. In high magnetic fields a biaxial nematic phase is induced with the shortest dimension of the particles aligned along the field. Moreover, if particles have a shape almost exactly in between rod-like and plate-like they can spontaneously, without external magnetic field, form biaxial nematic and biaxial smectic A phases, which is in accordance with theoretical predictions. The macroscopic domains were oriented by a magnetic field and their structure was revealed by small-angle X-ray scattering. Our results suggest that biaxial phases can be readily obtained by a proper choice of the particle shape.
TL;DR: In this article, the physical and electro-optical properties of FLCs after the doping of a dilute suspension of ferroelectric nanoparticles (BaTiO3) have been studied.
Abstract: The effects on the physical and electro-optical properties of ferroelectric liquid crystals (FLCs) after the doping of a dilute suspension of ferroelectric nanoparticles (BaTiO3) have been studied. Due to the permanent electric dipole moments of the ferroelectric nanoparticles, the spontaneous polarisation of FLCs with low doping concentration was about twice that of pure FLCs, in addition to a significant improvement in the dielectric properties, the response time and the V-shaped switching in the chiral smectic C (SmC∗) phase. The results obtained point the way to an alternative for improving the applicability of FLCs without resorting to chemical synthesis.
TL;DR: The phase transition behavior of the chiral liquid crystal CE6 doped with spherical surface functionalised CdSe nanoparticles has been examined by means of high-resolution adiabatic scanning calorimetry and polarising microscopy as mentioned in this paper.
Abstract: The phase transition behaviour of the chiral liquid crystal CE6 doped with spherical surface-functionalised CdSe nanoparticles has been examined by means of high-resolution adiabatic scanning calorimetry and polarising microscopy. The addition of nanoparticles results in an essentially stabilised blue phase III. The phase diagram is displayed upon heating and cooling and the enthalpy changes involved in the conversion between the blue phases are determined. The dispersion of functionalised nanoparticles is prominent for the stabilisation of blue phase III, which is potentially useful for applications, especially if applied on liquid crystals that exhibit blue phases close to room temperature.
TL;DR: In this article, four laterally difluorinated phenyl tolane liquid crystals were synthesized and their physical properties evaluated, and they were doped 10 wt% of each compound into a commercial negative mixture N1 and measured the birefringence, visco-elastic coefficient and figure of merit.
Abstract: Four laterally difluorinated phenyl tolane liquid crystals were synthesised and their physical properties evaluated. These compounds exhibit a fairly small heat fusion enthalpy (ΔH ∼ 12.56 kJ mol−1), which is favourable for mixture formulations. For comparison, four lateral difluoro cyclohexane tolane homologues are also studied. We doped 10 wt% of each compound into a commercial negative mixture N1 and measured the birefringence, visco-elastic coefficient and figure of merit. Birefringence varies very little between homologues, but the visco-elastic coefficient increases as alkyl chain length increases. The refractive indices of these guest–host mixtures at 1550 nm are also measured.
TL;DR: The mesomorphic properties of 4-alkylcyclohexyl-4-isothiocyanates are described in this article, and the synthesis and mesomorphic synthesis properties of 3-fluoro-3,5-difluorobiphenyl (3-5-DBF) and 4-kChenyl-2,4-hexyl (4-khexyl) are discussed.
Abstract: The syntheses and mesomorphic properties of 4-alkylcyclohexyl- and 4-alkylcyclohexylethyl and 4-alkylbicyclohexyl-3-fluoro- and 3,5-difluorobiphenyl-4-isothiocyanates are described. The compounds are low melting, very broad range nematic liquid crystals and are very useful for the formulation of nematic mixtures of low viscosity and with a moderately high birefringence (0.3–0.35). The refractive indices, bulk viscosity and dielectric anisotropy extrapolated from Demus' ester mixture for the prepared compounds are presented.
TL;DR: The thermal stability, alignment and electro-optic properties of liquid crystals can be fundamentally altered by dispersing small amounts of solid nanoparticles in a liquid crystal host as mentioned in this paper, and the local alignment of the liquid crystal in such dispersions is studied by means of polarising optical microscopy and fluorescence confocal polarising microscopy.
Abstract: The thermal stability, alignment and electro-optic properties of liquid crystals can be fundamentally altered by dispersing small amounts of solid nanoparticles in a liquid crystal host. In the present study, the local alignment of the liquid crystal in such dispersions is studied by means of polarising optical microscopy and fluorescence confocal polarising microscopy. The results of two- and three-dimensional imaging indicate that birefringent stripes, which are induced by the presence of nanoparticles, correspond to twist disclinations that are located at the liquid crystal–substrate interface. The luminescence of dispersed semiconductor quantum dots shows that the ends of disclination threads are pinned to conglomerates of nanoparticles, which stabilise these line defects.
TL;DR: In this paper, a series of new liquid-crystalline adducts of lanthanum tris(β-diketonates) displaying nematic and smectic mesomorphism was synthesized and investigated.
Abstract: A series of new liquid-crystalline adducts of lanthanum tris(β-diketonates) displaying nematic and smectic mesomorphism was synthesised and investigated. The temperatures and thermodynamic parameters of the phase transitions were determined. Even–odd alternation of the nematic–isotropic transition was observed in the series of synthesised complexes. It was found that films of the obtained liquid-crystal complexes are vitrified when cooling, and packings of molecules, formed in the mesophase, are retained. Interlayer distances were determined and a model of packing of molecules in the mesophase was suggested based on data obtained by a small-angle X-ray scattering method.
TL;DR: In this paper, the geometry of glycolipid assemblies with molecular packing constraints was analyzed based on the closest packing assumption and the surface area per molecule for straight and branched-chain alkyl glycosides with varying chain length was calculated.
Abstract: In an attempt to relate the geometry of glycolipid assemblies with molecular packing constraints, the surface areas per molecule for straight and branched-chain alkyl glycosides with varying chain length are calculated. Effects of temperature, water content, sugar size and paraffin chain length are analysed based on closest packing assumption. The results show a continuous increase of the interface between the hydrophilic and the hydrophobic domain per molecule with growing dominance in bulkiness of either domain, until it reaches a maximum in hexagonal phases. The surface area per molecule, on the other hand, exhibits a sudden jump upon the phase transition from a lamellar to a hexagonal phase, reflecting different values of the packing parameter in both assemblies. This increase is primarily based on the assembly, rather than on molecule-based domain sizes. Therefore, estimations of molecular region sizes can serve only to determine the principal ability of compounds to form certain phases, but not pred...
TL;DR: In this paper, the helical pitch of three ring chiral esters with terminal chains, one 1-methylheptyl group and one alkanoyloxyhexyloxy group, was measured by a spectrophotometric method of selectively reflected light.
Abstract: The homologous series of three ring chiral esters with terminal chains, one 1-methylheptyl group and, one alkanoyloxyhexyloxy group, were studied. Compounds of these series are liquid crystals with smectic phases, that is, SmA, SmC* (ferroelectric phase) and SmC*A (antiferroelectric phase). The helical pitch was measured by a spectrophotometric method of selectively reflected light. It was found that the helical pitch increases and then decreases with temperature in the SmC*A phase for most homologues and in the SmC* phase for one homologue. The temperature characteristics of the helical pitch are related to the change in handedness of the helix.
TL;DR: In this paper, a five-ring bent-core unit and a phenyl benzoate moiety are linked together by means of a flexible spacer, and the direction of each of the four ester connecting groups in the unit is reversed step by step.
Abstract: A five-ring bent-core unit and a phenyl benzoate moiety are linked together by means of a flexible spacer. Starting from dimers having different length of the aliphatic parts, that is the terminal alkyloxy chains and the spacer, the direction of each of the four ester connecting groups in the bent-core unit is reversed step by step. In this way thermodynamically stable polar and non-polar mesophases in unusual sequences could be obtained. For instance, a SmCsPAF–SmCs´PAF transition and the existence of two nematic phases (N, NX) have been observed. The nematic phases of the banana-calamitic dimers exhibit unusual properties comparable to those of the nematic phases reported for some monomeric bent-core mesogens. The electric field-induced enhancement of the SmCP–SmA transition temperature of one compound proves the existence of polar clusters already in the non-polar SmA phase.
TL;DR: A series of non-symmetric liquid crystal compounds consisting of two different semi-rigid anisometric cores, namely 1,3,4-oxidiazole and biphenyl units, and two short terminal groups, have been synthesized in good yield as discussed by the authors.
Abstract: A series of non-symmetric liquid crystal compounds consisting of two different semi-rigid anisometric cores, namely 1,3,4-oxidiazole and biphenyl units, and two short terminal groups, have been synthesised in good yield. It has been shown by polarising optical microscopy and differential scanning calorimetry that all these compounds display liquid crystalline behaviour, with nematic and/or smectic A mesophases. The nature of the mesophases is dependent on the electronic properties of the terminal groups. In methylene chloride solution all the compounds displayed a room temperature emission with λmax at 358–396 nm and quantum yields of 0.29–0.56. The effect of the terminal groups on the mesomorphic and photoluminescent properties is briefly discussed in the context of their electronic characteristics.
TL;DR: In this article, the authors review the recent numerical studies on possible defect structures when blue phase I (BP I) is confined in a thin cell composed of two parallel surfaces imposing homeotropic anchoring, and find several structures of disclination lines which, to their knowledge, have never been discussed in the field of liquid crystals as equilibrium structures.
Abstract: After an overview of cholesteric blue phases, we review our recent numerical studies on possible defect structures when blue phase I (BP I) is confined in a thin cell composed of two parallel surfaces imposing homeotropic anchoring. The cell thickness is of the order of the unit cell dimension of the bulk cubic BP I. We find several structures of disclination lines which, to our knowledge, have never been discussed in the field of liquid crystals as equilibrium structures. Those structures include a parallel array of double helix disclination lines, and two parallel arrays of undulating disclination lines almost (but not exactly) perpendicular to each other. A first-order transition between those two structures is possible, and the similarity between them is discussed.
TL;DR: In this paper, a single-layer polymer-stabilised liquid crystal (PSLC) film reflecting both right and left-circularly polarised light has been developed by a washout/refill method.
Abstract: In this study, a single-layer polymer-stabilised liquid crystal (PSLC) film reflecting both right- and left-circularly polarised light has been developed by a wash-out/refill method. A polymer network/liquid crystals (LCs) composite, in which the polymer network had a certain helical structure, was prepared by photo polymerisation of the photo-polymerisable LC monomers (LCMs) in a LCM/LC/photoinitiator mixture. Then, the LC molecules were extracted from the composite film and cholesteric LCs (Ch-LCs) with the opposite helical structure were refilled into the film. The film was constructed by the polymer network with a certain helical structure and Ch-LCs with the opposite helical structure could reflect both right- and left-circularly polarised light simultaneously. The reflection intensity of the film is close to 100% when the pitch lengths of the two opposite helical structures are the same, which goes beyond the 50% reflectance limit of Ch-LCs. It was demonstrated that the memory effect of the polymer ...
TL;DR: In this article, an efficient synthetic method for C3-symmetrical truxene derivative was developed for polymesomorphism and organic semiconductor candidates, which can be applied to truxenes.
Abstract: Truxene discotic liquid crystals are interesting for their polymesomorphism and as organic semiconductor candidates. We developed an efficient synthetic method for C3-symmetrical truxene derivative...
TL;DR: In this paper, simple analytic solutions to the equations governing the nematic liquid crystal director profiles under an external voltage and arbitrary anchoring energy, taking into consideration the non-uniform field distribution, are presented.
Abstract: Simple analytic solutions to the equations governing the nematic liquid crystal director profiles under an external voltage and arbitrary anchoring energy, taking into consideration the non-uniform field distribution, are presented. Exact numerical results are compared to the analytic solutions showing good agreement particularly for the case of strong anchoring. The usefulness of the approximate analytic solutions is remarkable for the quick design of liquid crystal devices and understanding the dependence of the optical response on voltage and material parameters.
TL;DR: In this paper, two groups of the title compounds were prepared and investigated for their mesophase formation and stability, and the difference between them lies in the orientation protrusion of the lateral methyl group attached to the central benzene ring.
Abstract: Two groups of the title compounds were prepared and investigated for their mesophase formation and stability. Each group constitutes five homologous series that differ from each other by the polar substituent X (CH3O, CH3, H, Cl, and NO2). Within each homologous series, the number (n) of carbons in the alkoxy chain varies between 8, 10, 12, 14 and 16. The difference between the two groups of compounds lies in the orientation protrusion of the lateral methyl group attached to the central benzene ring. In the first group (Group I) the methyl substituent, introduced into the o-position with respect to the ester group, makes an angle of 60° with the long axis of the molecule. In the other series of compounds (Group II), the orientation angle is 120° as it is introduced into the position-3. All possible binary phase diagrams could be constructed in which the two components are corresponding positional isomers from either group. The study aimed to investigate the effect of inclusion of the lateral methyl group,...
TL;DR: In this article, four short chain members of the copper(II) n-alkanoate series Cu(Cn)2, from propanoate to hexanoate, have been synthesized, purified and characterized by means of optical microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR and Raman spectroscopy.
Abstract: Four short chain members of the copper(II) n-alkanoate series Cu(Cn)2, from propanoate to hexanoate, have been synthesized, purified and characterized by means of optical microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR and Raman spectroscopy. The TGA study shows that decomposition starts on heating above 420–470 K (depending on the sample) in a nitrogen atmosphere. In addition, thermal decomposition was investigated by DSC using special high pressure pans and endo- and exc-thermic processes were found which have not been reported previously. All but one of the compounds melt to a liquid crystal phase, which decomposes before the clearing point. The exception is the propanoate homologue, which decomposes directly from the solid state. Despite this problem of sample decomposition, the identification by optical microscopy of the tetragonal (butanoate) and hexagonal (pentanoate and hexanoate) discotic columnar phases was, for first time, possible by the addition of ...
TL;DR: In this paper, a polymer-stabilised cholesteric liquid crystal (PSChLC) was fabricated by ultraviolet (UV) induced polymerisation of photopolymerisable acrylate monomers mixed in a ChLC, and a hydrogen bond, arising between the polymer network with a concentration gradient containing carboxyl as proton donors and chiral dopant (CD) as propton acceptors, induced a pitch gradient in PSChLC and then, as a consequence, broadband reflection.
Abstract: A polymer-stabilised cholesteric liquid crystal (PSChLC) was fabricated by ultraviolet (UV) induced polymerisation of photopolymerisable acrylate monomers mixed in a cholesteric liquid crystal (ChLC). A polymer network with a concentration gradient, which was induced by UV light absorption of dye along the propagation direction, was formed. A hydrogen bond, arising between the polymer network with a concentration gradient containing carboxyl as proton donors and chiral dopant (CD) as proton acceptors, induced a pitch gradient in PSChLC and then, as a consequence, broadband reflection. The broadband reflection is associated with the concentration and the composition of photopolymerisable acrylate monomers, the concentration of CD and the polymerisation temperature. Examining the morphologies of the polymer network by scanning electron microscopy, the helix structure and pitch gradient were verified, confirming the pitch gradient of the PSChLC and revealing the essence of the formation of broadband reflection.