Supramolecular complexes based on liquid‐crystalline polysiloxanes and copper phthalocyanine

Self‐assembly of mesogens in one polymer system reflects the capability for integrating intermolecular interactions and functions of materials. A series of novel supramolecular complexes (SCPs) containing cholesterol derivatives, siloxane backbone and copper phthalocyanine were synthesized. The SCPs were made from sulfonic acid‐containing precursor polymers (SAPs) synthesized by the use of 4‐(allyloxy)benzenesulfonic acid, cholest‐5‐en‐3‐ol‐(3β)‐4‐(allyloxy)benzoate and polymethylhydrosiloxane. Differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction results confirmed the mesomorphic properties. The SAPs showed smectic phase, but the SCPs showed columnar phase due to more lateral copper phthalocyanine groups in the polymer systems. Moreover, because of rigid side groups and cholesteric polymer, SCPs showed greater d‐spacings between the side mesogenic groups and exhibited very good electrical conductivity. © 2018 Society of Chemical Industry     

Composition effects on ion transport in a polyelectrolyte gel with the addition of ion dissociators

The polymerization of lithium 2-acrylamido-2-methyl-1-propane sulphonic acid with N,N′-dimethylacrylamide has yielded polyelectrolyte gels which have the favourable property of being single ion conductors. The use of single ion conductors ensures that the transport number of lithium is close to unity. The mobility of the lithium ion is still quite low in these systems, resulting in low ionic conductivity. To increase ionic conductivity more charge carriers can be added however competing effects arise between increasing the number of charge carriers and decreasing the mobility of these charge carriers. In this paper the monomer ratio of the copolymer polyelectrolyte is varied to investigate the effect increasing the number of charge carriers has on the ionic conductivity and lithium ion and solvent diffusivity using pfg-NMR. Ion dissociators such as TiO₂ nano-particles and a zwitterionic compound based on 1-butylimidazolium-3-(N-butanesulfonate) have been added in an attempt to further increase the ionic conductivity of the system. It was found that the system with the highest ionic conductivity had the lowest solvent mobility in the presence of zwitterion. Without zwitterion the mobility of the solvent appears to determine the maximum ionic conductivity achievable.     

Dielectric and conductivity studies on cobalt phthalocyanine tetramers

Electrically conductive organic and metalloorganic polymers are of great interest and they have applications in electronic, optical, photonic, photoelectric, electrochemical, and dielectric devices. Tetrameric cobalt phthalocyanine was prepared by conventional chemical method. The dielectric permittivity of the tetrameric cobalt phthalocyanine sample was evaluated from the observed capacitance values in the frequency range 100 KHz to 5 MHz and in the temperature range of 300 to 383°K. It is found that the system obeys the Maxwell Wagner relaxation of space charge phenomenon. Further, from the permittivity studies AC conductivity was evaluated. The values of AC conductivity and DC conductivity were compared. Activation energy was calculated. To understand the conduction mechanism Mott's variable range hopping model was applied to the system. The T^?1/4 behavior of the DC conductivity along with the values of Mott's Temperature (T₀), density of states at the Fermi energy N (E_F), and range of hopping R and hopping energy W indicate that the transport of charge carriers are by three‐dimensional variable range hopping. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2529–2535, 2004     

Chemical oxidative grafting of conducting poly(N‐methyl aniline) onto poly(ethylene terepthalate)

Detailed studies on the peroxidisulfate (PDS) initiated graft copolymerization of N‐methyl aniline (NMA) with poly(ethylene terepthalate) (PET) were carried out in p‐tolene sulfonic acid medium under nitrogen atmosphere. Experiments were designed to follow the rate of formation R_h of the poly(N‐methyl aniline (PNMA), simultaneously with the rate of grafting of PNMA onto PET. Effects of concentration of NMA, PDS, PET, time, and temperature on R_h and graft parameters were followed. Kinetic equations were deduced to correlate the changes in the rate with experimental conditions. Graft copolymers were isolated and grafting of PNMA onto PET was confirmed through FTIR, thermogravimetric analysis, and conductivity measurements. Tensile measurements showed that grafting of PNMA did not alter the tensile properties of PET. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 596–605, 2005     

Local coordination,electronic structure,and thermal quenching of Ce3+ in isostructural Sr2GdAlO5 and Sr3AlO4F phosphors

Sr₂GdAlO₅:Ce and Sr₃AlO₄F:Ce are isostructural phosphors in which the Ce³⁺ 4f-5d₁ transition can be efficiently excited by a photon with energy lower than 3.1 eV. Herein, we analyze the crystal chemistry of the Ce³⁺ local coordination, compare the thermal quenching behavior and construct the electronic structure of Ce³⁺ in them. The Rietveld refinement on two occupancy models suggests that Gd³⁺ only occupies the 8h site in Sr₂GdAlO₅; this provides a hint on the preferred occupancy of dopant Ce³⁺ in this site. The large crystal filed splitting of Ce_8h is mainly due to the fact that the 8h site is bonded to two oxygen with relatively short d_Sr/Gd-O and forms a quasi-square antiprism which experiences a large distortion. The Ce³⁺ 5d-4f luminescence in Sr₃AlO₄F is much more stable against thermal quenching than that in Sr₂GdAlO₅, as evidenced by the temperature-dependent luminescence intensity and luminescence decay studies. The energy of the O²⁻-Eu^3+/2+ and O²⁻-Ce^4+/3+ charge transfer as well as bandgap were estimated and the electronic structure of Ce³⁺ were constructed. A larger energy barrier ΔE_dC between the Ce³⁺ 5d₁ level and the conduction band bottom in Sr₃AlO₄F is seen from the Vacuum Referred Binding Energy (VRBE) diagrams which explains the higher thermal quenching temperature by thermal ionization model.     

Novel sulfonated poly(arylene biphenylsulfone ether) copolymers containing bisphenylsulfonyl biphenyl moiety: structural,thermal, electrochemical and morphological characteristics

A series of sulfonated poly(arylene biphenylsulfone ether) polymers containing up to two pendant sulfonic acid groups per repeat unit were successfully synthesized from 4,4′‐bis[(4‐chlorophenyl)sulfonyl]‐1,1′‐biphenyl (BCPSBP), disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenylsulfone (SDCDPS) and bisphenol A via aromatic nucleophilic displacement polycondensation. The resulting polymers were characterized by means of Fourier transform infrared and ¹H NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis (TGA). The number‐average molecular weight (M_n) of the synthesized polymers was in the range 15 300–22 900 g mol^?1, and the polydispersity indices (M_w/M_n) varied from 2.5 to 4.4. Tough membranes with SDCDPS/BCPSBP mole ratio up to 50:50 were successfully cast using N‐methyl‐2‐pyrrolidone (NMP). An increase of sulfonic acid groups in the polymer backbone resulted in increased solubility in aprotic polar solvents and glass transition temperature. The TGA curves of all the copolymers in acid form exhibited two distinct weight‐loss profiles. The influential characteristics of the polymer electrolyte membranes, such as tensile strength, water uptake, ion‐exchange capacity and proton conductivity, were characterized with respect to the pendant sulfonic acid groups. Atomic force microscopy phase images of the acid‐form membranes clearly showed the hydrophilic domains, with sizes increasing as a function of the degree of sulfonation. Copyright © 2010 Society of Chemical Industry     

Structure-property relationship of thermotropic liquid-crystalline vinyl polymers containing no traditional mesogen

A series of non-mesogenic vinyl monomers, 2,5-bis(alkoxycarbonyl)styrene, were synthesized and polymerized via free radical polymerization. The alkoxy groups were systematically varied to investigate the effects of their size and architecture on the thermotropic liquid-crystalline properties of the resultant polymers. Although no traditional mesogen was present in the macromolecular structure, all the polymers revealed stable hexagonal columnar liquid-crystalline phase at the temperatures well above their glass transitions when the molecular weights were high enough, as evidenced by a combinatory analysis of differential scanning calorimetry, polarized light microscopy, and one- and two-dimensional wide-angle X-ray diffraction techniques. For the polymers containing five carbon atoms in the alkoxy terminals, the temperatures of glass transition and mesophase formation decreased and the d-spacing value of mesophase increased as the methyl substituent moved away from the connecting phenyl ring. Increasing the number of methyl group or the size of the substituent had the same effect. In the case of polymers with Y-shaped alkoxy terminals, the larger the side groups, the lower the glass-transition temperature and mesophase formation temperature and the larger the d-spacing value of mesomorphic structure.     

Intercalation of conducting poly(N‐propane sulfonic acid aniline) in V2O5 xerogel

Poly(N‐propane sulfonic acid aniline) (PSPAN) can be formed between the lamellas of V₂O₅ xerogel by in situ oxidative polymerization/intercalation of N‐propane sulfonic acid aniline in the presence of air (V₂O₅ being the oxidation agent). The PSPAN/V₂O₅ nanocomposites were characterized by XRD, TEM, TGA, FTIR, UV–vis‐NIR, and conductivity measurement. The results show that the V₂O₅ maintains lamellar structure, but its interlayer spacing has increased from 1.18 to 1.31 nm. The FTIR spectra indicate that there is interaction between negatively charged oxygen of the sulfonic group of PASPN and the vanadium ion in V₂O₅ matrix. The electrical conductivity of PSPAN/V₂O₅ nanocomposite reached the value of 1.2 × 10^?2 S/cm, which is 10⁴ times higher than that of the V₂O₅ xerogel, and is 10² times more than that of the PSPAN. It was found that the aging in air facilitated the chain growth of PSPAN between the V₂O₅ lamellas, resulting in the increase of the electrical conductivity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2569–2574, 2007     

EPR study of polyaniline highly doped by p-toluenesulfonic acid

Magnetic, relaxation and electronic dynamic parameters of paramagnetic centers in crystalline domains of polyaniline highly doped by p-toluenesulfonic acid (PANI-PTSA) as well as PANI-PTSA dispersed in poly(methyl methacrylate) (PANI-PTSA/PMMA) were studied by the 3-cm (9.7 GHz) and 2-mm (140 GHz) wavebands EPR. At both wavebands these polymers demonstrate the Lorentzian single line with the Dysonian contribution indicating intrinsic conductivity of metal-like domains ca. 1500-4000 S/cm at room temperature. Effective conductivity of the polymer is defined by Q3D delocalization of charge carriers within such domains and their Mott variable range hopping between the domains dominating its micro- and macroscopic conductivity. It was shown that the interaction of the charge carriers with the lattice phonons governs the intradomain charge transfer at high temperatures. Dimensionality of the system increases with the polymer dispersion in an insulating matrix. Dipole-dipole interaction of polarons with oxygen biradicals reversibly changes the relaxation of the spins in the initial and dispersed polymers. These paramagnetic centers strongly interact below and weakly above critical temperature T_c of the phase transition that leads to an extremal temperature dependence of the polymer linewidth. The dependence of T_c on electron precession frequency and/or on the PANI-PTSA dispersion in an insulating matrix was revealed. Spin relaxation and dynamics were analyzed to be non-correlated with charge transfer in PANI-PTSA that contradicts the “single conducting chain” model and justifies the formation of Q3D metal-like domains.     

Synthesis and characterization of poly(N‐methyl aniline) doped with sulphonic acids: Their application as humidity sensors

Single step chemical polymerization of N‐methyl aniline was carried out by using ammonium persulphate as an oxidizing agent. The conducting emeraldine salt phase of the polymers using camphor sulfonic acid and p‐toluene sulfonic acid as dopants was made by a direct process. The polymers were characterized by UV‐vis and FTIR spectroscopy, scanning electron microscopy, TGA, and conductivity measurements. The synthesized polymers were found to have very good physicochemical properties and good electrical conductivity. Conductivity measurements have shown “thermal activated behavior.” The change in resistance with respect to % relative humidity (RH) was observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20 and 100% RH). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 812–820, 2006     

High piezoelectric sensitivity and hydrostatic figures of merit in unidirectional porous ferroelectric ceramics fabricated by freeze casting

High performance lead zirconate titanate (PZT) ceramics with aligned porosity for sensing applications were fabricated by an ice-templating method. To demonstrate the enhanced properties of these materials and their potential for sensor and hydrophone applications, the piezoelectric voltage constants (g₃₃ and g₃₁), hydrostatic parameters (d_h, g_h, ?d₃₃/d₃₁, d_h·g_h and d_h·g_h/tanδ) and AC conductivity as a function of the porosity in directions both parallel and perpendicular to the freezing temperature gradient were studied. As the porosity level was increased, PZT poled parallel to the freezing direction exhibited the highest d_h, ?d₃₃/d₃₁ and figures of merit d_h·g_h, d_h·g_h/tanδ compared to the dense and PZT poled perpendicular to the freezing direction. The g_h, g₃₃ and g₃₁ coefficients were highest for the PZT poled perpendicular to the freezing direction; the g_h was 150%–850% times higher than dense PZT, and was attributed to the high piezoelectric activity and reduced permittivity in this orientation. This work demonstrates that piezoelectric ceramics produced with aligned pores by freeze casting are a promising candidate for a range of sensor applications and the polarisation orientation relative to the freezing direction can be used to tailor the microstructure and optimise sensitivity for sensor and hydrostatic transducer applications.     

Preparation and properties of waterborne polyurethane/polyaniline codoped with dodecyl benzene sulfonic acid and hydrochloric acid blends

A conductive poly(aniline codoped with dodecyl benzene sulfonic acid and hydrochloric acid) [PANI‐D/H, yield: 32.2%, intrinsic viscosity ([η]): 1.39 dL/g, electrical conductivity: 7.3 S/cm] was synthesized by chemical oxidative polymerization from aniline‐dodecylbenzene sulfonic acid salt (A‐DS)/aniline‐hydrochloric acid salt (A‐HS) (6/4M ratio) in an aqueous system. Waterborne polyurethane (WBPU) dispersion obtained from isophorone diisocyanate/poly(tetramethylene oxide)glycol/dimethylol propionic acid/ethylene diamine/triethylene amine/water was used as a matrix polymer. The blend films of WBPU/PANI‐D/H with various weight ratios (99.9/0.1–25/75) were prepared by solution blending/casting. Effect of PANI‐D/H content on the mechanical property, dynamic mechanical property, hardness, electrical conductivity, and antistaticity of WBPU/PANI‐D/H blend films was investigated. The dynamic storage modulus and initial tensile modulus increased with increasing PANI‐D/H content up to 1 wt %, and then it was significantly decreased about the content. With increasing PANI‐D/H content, the glass transition temperature of soft segment (T_gs) and hard segment (T_gh) of WBPU/PANI‐D/H blend films were shifted a bit to lower the temperature. The tensile strength and hardness of WBPU/PANI‐D/H blend films increased a little with increasing PANI‐D/H content up to 0.5 wt %, and then it was dramatically decreased over the content. The elongation at break of WBPU/PANI‐D/H decreased with an increase in PANI‐D/H content. From these results, it was concluded that 0.5–1 wt % of PANI‐D/H was the critical concentration to reinforce those various properties of WBPU/PANI‐D/H blend films prepared in this study. The electrical conductivity of WBPU/ultrasonic treated PANI‐D/H (particle size: 0.7 μm) blend films prepared here increased from 4.0 × 10^?7 to 0.33 S/cm with increasing PANI‐D/H content from 0.1 to 75 wt %. The antistatic half‐life time (τ_1/2) of pure WBPU film was about 110 s. However, those of WBPU/ultrasonic treated PANI‐D/H blend films (τ_1/2: 8.2–0.1 s, and almost 0 s) were found to decrease exponentially with increasing PANI‐D/H content (0.1–9 wt %, and above 9 wt %). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 700–710, 2004     

Synthesis of high molecular weight polyoxyethylene with a quaternary catalyst and study of its conductive blends with poly(2‐vinyl pyridine)

High molecular weight polyoxyethylene (PEO) was synthesized by using a quaternary catalyst composed of triisobutyl aluminum, phosphoric acid, water, and N,N‐dimethylaniline (DMA). Optimum synthesis conditions and some properties of the product were studied. This catalyst showed high activity and the molecular weight of the polyoxyethylene obtained can approach one million. The activity of polymerization mainly depends upon the composition of catalyst. The optimum composition is as follows: i‐Bu₃Al:H₃PO₄:H₂O:DMA = 1 : 0.17 : 0.17 : 0.10–0.15 (molar ratio).The active centers of the catalyst was thus proposed. The high molecular weight PEO synthesized by this catalyst was blended with poly(2‐vinyl pyridine) (PVP) and then doped with LiClO₄ and TCNQ to obtain a conductive elastomeric material. Ionic, electronic, and mixed (ionic–electronic) conductivities of blends were investigated. At a Li/EO molar ratio of 0.1 and a TCNQ/VP molar ratio of 0.5, the mixed conductivity of the blend of PEO/PVP/LiCIO₄/TCNQ is higher than the sum of ionic conductivity of PEO/PVP/LiCIO₄ and electronic conductivity of PEO/PVP/TCNQ, when the weight ratio of PEO to PVP is 6/4 or 5/5. It can reach 4 × 10^?6 S/cm at room temperature. Differential scanning calorimetry, thermal gravimetric analysis, and the appearance of the blend showed that both TCNQ and LiClO₄ can complex with PEO and PVP, thus enhancing the compatibility between PEO and PVP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanism of superior charge suppression behavior of Si3N4 ceramics at solid-gas interface

Recent study has found excellent bulk and surface insulation property of Si₃N₄ ceramic which make it potential to serve as key insulation component in various energy transmission apparatus. Charge accumulation at gas-solid interface is a critical insulation property but few relevant study on Si₃N₄ can be found. This contribution has investigated the surface charge property of Si₃N₄ ceramic compared to traditional insulation polymer under different electrical-thermal stress. Through its comparison with the electric field distribution, the main source of the surface charge accumulation is analyzed, indicating that the superior surface charge suppression performance of Si₃N₄ lies on its low carrier density and conduction barrier, which considerably prevent charge injection and suppress the normal electric field which drives the charge to the gas-solid interface. The proposed mechanism is also validated by the characterization on conducting and space charge property for Si₃N₄ as well as dynamic simulation on surface charge accumulation.     

Synthesis and characterization of poly(o‐toluidine) doped with organic sulfonic acid by solid‐state polymerization

Poly (o‐toluidine) (POT) salts doped with organic sulfonic acids (β‐naphthalene sulfonic acid, camphor sulfonic acid, and p‐toluene sulfonic acid) were directly synthesized by using a new solid‐state polymerization method. The FTIR spectra, ultraviolet visibility (UV–vis) absorption spectra, and X‐ray diffraction patterns were used to characterize the molecular structures of the POT salts. Voltammetric study was done to investigate the electrochemical behaviors of all these POT salts. The FTIR and UV–vis absorption spectra revealed that the POT salts were composed of mixed oxidation state phases. All POT salts contained the conducting emeraldine salt (half‐oxidized and protonated form) phase; the pernigraniline (fully oxidized form) phase is predominant in POT doped with β‐naphthalene sulfonic acid, and POT doped with p‐toluene sulfonic acid had the highest doping level. The X‐ray diffraction patterns showed that the obtained POT doped with organic sulfonic acids were lower at crystallinity. The conductivity of the POT salts were found to be of the order 10^?3‐10^?4 S/cm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1630–1634, 2005     

Protonation of polyaniline by surface-functionalized polymer substrates

The protonation of solution-coated emeraldine (EM) base by sulfonic and carboxylic acid groups on surface-functionalized low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and conductivity measurements. Surface functionalizations were achieved by sulfonation (for LDPE, HDPE, PP, and PET), by hydrolysis (for PET), and by near-UV-light-induced surface graft copolymerization with the Na salt of styrene sulfonic acid and acrylic acid (for all substrates). The efficiency of surface functionalization by graft copolymerization is substantially enhanced for substrates pretreated with O₃ or Ar plasma. Protonation levels of 50% can be readily achieved for EM coated on sulfonic acid, but not carboxylic acid, functionalized surfaces. The extent of protonation, however, is also dependent on the microstructures of the modified substrate surfaces. In all cases, charge transfer interactions between the EM layer and the functionalized substrates readily result in good adhesion of the electroactive polymer on the polymer substrates to give rise to conductive surface structures. © 1995 John Wiley & Sons, Inc.     

Organic‐acid‐catalyzed sol–gel route for preparing poly(methyl methacrylate)–silica hybrid materials

In this study, a series of organic–inorganic hybrid sol–gel materials consisting of a poly(methyl methacrylate) (PMMA) matrix and dispersed silica (SiO₂) particles were successfully prepared through an organic‐acid‐catalyzed sol–gel route with N‐methyl‐2‐pyrrolidone as the mixing solvent. The as‐synthesized PMMA–SiO₂ nanocomposites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and condensation (i.e., sol–gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid membranes was beneficial for the physical properties at low SiO₂ loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molecular permeability, optical clarity, and surface morphology of the as‐prepared hybrid PMMA–SiO₂ nanocomposites in the form of membranes were investigated with thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet–visible transmission spectroscopy, and atomic force microscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Solubility and electrochemical properties of chemically modified polyaniline‐gold/camphor sulfonic acid composites

Polyaniline nanocomposites encapsulating gold nanoparticles on camphor sulfonic acid (CSA) surface were prepared via the polymerization of aniline hydrochloride with different concentrations of CSA using HAuCl₄ as oxidant. The synthesized composites were characterized by Fourier transform infrared spectroscopy and UV–visible spectroscopy. Surface morphology was studied by scanning electron microscopy and transmission electron microscopy. The embedded crystallinity of the composites was investigated by X‐ray diffraction analysis. The solubility of the nanocomposites was studied using water, N‐methyl‐2‐pyrrolidinone, chloroform, and dimethylformamide solvents. The room temperature direct current conductivity of the composites was also observed in solution state. Electrical property of the composites was examined using cyclic voltammetric measurements at room temperature. The fabricated polymer nanocomposites with better solubility in water and some organic solvents will have various applications in electrical devices and biosensors. POLYM. COMPOS., 36:245–252, 2015. © 2014 Society of Plastics Engineers     

Current–voltage–temperature characteristics for 2D arrays of metallic quantum dots

Computational results for the temperature-dependent conductivity of compressed arrays of size-selected Ag nanodots are discussed. Special attention is given to the role of phase transitions of the array as a function of external control variables: the applied voltage, the temperature, and the compression of the array. The computations are based on a scattering formalism that is presented in detail so that all the assumptions are explicitly spelled out. The results demonstrate the ability of low-lying excited electronic states of 2D lattices to probe by temperature-dependent conductivity measurements.     

Camphor sulfonic acid doped polyaniline-tin oxide hybrid nanocomposites: Synthesis,structural, morphological,optical and electrical transport properties

Camphor sulfonic acid (CSA) doped PANi–SnO₂ hybrid nanocomposites were synthesized by solid-state synthesis route with varying amounts (10–50%) of CSA. X-ray diffraction studies have proven the successful incorporation of CSA into the polyaniline–SnO₂ hybrid nanocomposites and the results are also supported by microstructural analysis. UV–visible and Fourier infrared spectroscopy studies have provided insight into the electronic interaction between the CSA, polyaniline, and SnO₂. The room temperature dc electrical conductivity of CSA-doped PANi–SnO₂ hybrid nanocomposite films were observed to depend on the amount of CSA doping and the morphology.