Login In
2001 Volume 19 Issue 3
2001, 19(3): 237-246
Abstract:
Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differentialscanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, tofit the primary stage of isothermal and nonisothermal crystallizations of nylon 66, In the isothermal crystallization process,mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determinedfrom the Lauritzen-Hoffman treatment are σ=9.77 erg/cm2 and σe=155.48 erg/cm2,respectively;and the work of chain folding is q=33.14 kJ/mol.The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo methof combined with the Avrami and Ozawa equations.The average Avrami exponent ? was determined to be 3.45.The activation energies(△E) were determined to be -485.45 kJ/mol -331.27 kJ/mol,respectively,for the isothermal and nonisothermal crystallization processes by the Arrhenius and the Kissinger methods.
Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differentialscanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, tofit the primary stage of isothermal and nonisothermal crystallizations of nylon 66, In the isothermal crystallization process,mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determinedfrom the Lauritzen-Hoffman treatment are σ=9.77 erg/cm2 and σe=155.48 erg/cm2,respectively;and the work of chain folding is q=33.14 kJ/mol.The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo methof combined with the Avrami and Ozawa equations.The average Avrami exponent ? was determined to be 3.45.The activation energies(△E) were determined to be -485.45 kJ/mol -331.27 kJ/mol,respectively,for the isothermal and nonisothermal crystallization processes by the Arrhenius and the Kissinger methods.
2001, 19(3): 247-253
Abstract:
The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface.Four kinds of perpendicular disclinations,i.e. χ→τ-+λ+,χ→λ-+τ+,χ→τ-+τ+ and χ→λ-+λ+, were found in the composite films from SEM observations.The smallest periodicity of lamellar-like structure(equals to half pitch)is 20～40 nm measured with AFM.
The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface.Four kinds of perpendicular disclinations,i.e. χ→τ-+λ+,χ→λ-+τ+,χ→τ-+τ+ and χ→λ-+λ+, were found in the composite films from SEM observations.The smallest periodicity of lamellar-like structure(equals to half pitch)is 20～40 nm measured with AFM.
2001, 19(3): 255-263
Abstract:
Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. Thelevels of birefringence signal are found to depend on the polarization angle between the pump beam and the probe beam, andon the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described byknown biexponential equations. The rate constants and the amplitudes associated with the growth process of thephotoinduced birefringence are observed to display a linear dependence with the pump beam intensity.A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the trans and cis isomers of azobenzene groups and the local polymer segments.The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.
Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. Thelevels of birefringence signal are found to depend on the polarization angle between the pump beam and the probe beam, andon the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described byknown biexponential equations. The rate constants and the amplitudes associated with the growth process of thephotoinduced birefringence are observed to display a linear dependence with the pump beam intensity.A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the trans and cis isomers of azobenzene groups and the local polymer segments.The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.
2001, 19(3): 265-268
Abstract:
When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystalfilm were successfully performed without disturbing the surface morphology.
When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystalfilm were successfully performed without disturbing the surface morphology.
2001, 19(3): 269-276
Abstract:
Sulfonated syndiotactic polystyrene ionomers (SsPS) with 1.8 mol% degree of sulfonation have been studied.WAXD shows that the crystallinity of SsPS ionomers was decreased with increasing diameter size of the counter ions andsPS>SsPS-H>SsPS-K>SsPS-Zn. Moreover, SsPS ionomers only have a α cystal form, while original sPS has two crystalforms: α and β crystal form. TGA shows that the thermal stability of SsPS ionomers is higher than that of the original sPSand SsPS-Zn>SsPS-K>SsPS-H. DSC shows that all the glass transition temperatures(Tg) of SsPS ionomers are higher than that of the neat sPS and SsPS-Zn>SsPS-Na>SsPS-K>SsPS-H.However,the melting temperature (Tm) and crystallization peak temperature (Tp of SsPS ionomers are lower and SsPS-H>SsPS-Zn>SsPS-K>SsPS-Na,while the crystallinity(Xc) of SsPS-Zn is the lowest.Nonisothermal crystallization kinetics shows that the Avrami index of sPS and SsPS-H are both about 4,suggesting the mucleation growth of SsPS-H with lower degree of sulfonation still keeps its three-dimension form.FTIR spectra of SsPS ionomers show a splitting absorption band for asymmetric stretching vibration of sulfonation group.The CH in-plane bending vibration of benzene ring shifted to higher wavenumber and the symmetric streching vibration of sulfonation group changed slightly with different counter ion neutralized SsPS ionomers.
Sulfonated syndiotactic polystyrene ionomers (SsPS) with 1.8 mol% degree of sulfonation have been studied.WAXD shows that the crystallinity of SsPS ionomers was decreased with increasing diameter size of the counter ions andsPS>SsPS-H>SsPS-K>SsPS-Zn. Moreover, SsPS ionomers only have a α cystal form, while original sPS has two crystalforms: α and β crystal form. TGA shows that the thermal stability of SsPS ionomers is higher than that of the original sPSand SsPS-Zn>SsPS-K>SsPS-H. DSC shows that all the glass transition temperatures(Tg) of SsPS ionomers are higher than that of the neat sPS and SsPS-Zn>SsPS-Na>SsPS-K>SsPS-H.However,the melting temperature (Tm) and crystallization peak temperature (Tp of SsPS ionomers are lower and SsPS-H>SsPS-Zn>SsPS-K>SsPS-Na,while the crystallinity(Xc) of SsPS-Zn is the lowest.Nonisothermal crystallization kinetics shows that the Avrami index of sPS and SsPS-H are both about 4,suggesting the mucleation growth of SsPS-H with lower degree of sulfonation still keeps its three-dimension form.FTIR spectra of SsPS ionomers show a splitting absorption band for asymmetric stretching vibration of sulfonation group.The CH in-plane bending vibration of benzene ring shifted to higher wavenumber and the symmetric streching vibration of sulfonation group changed slightly with different counter ion neutralized SsPS ionomers.
2001, 19(3): 277-282
Abstract:
Ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid (AA) becomes a cholesteric liquid crystalline solution withvivid colors when the (E-CE)C concentration is 42 wt%～52 wt%. (E-CE)C/polyacrylic acid (PAA) composites withcholesteric structure were prepared by polymerzing AA in (E-CE)C/AA liquid crystalline solutions. The layers of orderedpolymer chains in the cholesteric phase were inclined during polymerization and the degree of the inclination depended onthe polymerization temperature and the concentration of the solution before polymerization.The cholesteric structure in the composites could not be changed when temperature was lower than 100℃.Cross-linking of the PAA in composites improved their water-resistance.The cholesteric order of the composites without cross-linking was destroyed when they where immersed in water.The color derived from the selective reflection of the cholesteric phase of the cross-linked composites turned from blue to red after the composites absorbed water.The color of the composites could be returned to the original one when the absorbed water was removed from the swollen composites.
Ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid (AA) becomes a cholesteric liquid crystalline solution withvivid colors when the (E-CE)C concentration is 42 wt%～52 wt%. (E-CE)C/polyacrylic acid (PAA) composites withcholesteric structure were prepared by polymerzing AA in (E-CE)C/AA liquid crystalline solutions. The layers of orderedpolymer chains in the cholesteric phase were inclined during polymerization and the degree of the inclination depended onthe polymerization temperature and the concentration of the solution before polymerization.The cholesteric structure in the composites could not be changed when temperature was lower than 100℃.Cross-linking of the PAA in composites improved their water-resistance.The cholesteric order of the composites without cross-linking was destroyed when they where immersed in water.The color derived from the selective reflection of the cholesteric phase of the cross-linked composites turned from blue to red after the composites absorbed water.The color of the composites could be returned to the original one when the absorbed water was removed from the swollen composites.
2001, 19(3): 283-289
Abstract:
Fractions of a water insoluble α-(1→3)-D-glucan (GL) extracted from Ganoderma lucidum were carboxy-methylated (CM) to obtain water-soluble carboxymethylated derivatives (CM-GL) having a degree of substitution (DS) of 0.38～0.51. Weight-average molecular weight Mw and intrinsic viscosity [η] of the samples CM-GL were measured by gelpermeation chromatography combined with laser light scattering (GPC-LLS) and viscometry. The CM-GL exhibits a stifferchain in aqueous solution at 25℃ than the original glucan. The antitumor activities against Ehrlich ascites carcinoma(EAC,5×106) of the carboxymethylated derivatives from the α-glucan and curdlan,a β-glucan,are significantly higher than those of the original glucans.The effects of the relatively low molecular weight,expanded chains and better water-solubility of the CMM-GL on the enhancement of antitumor activity could not be neglected.The chain stiffness decreased speedily with increase of temperature from 40 to 60℃ or NaOH concentration from 0.1 to 0.4 in the solution,respectively,and the change of the chain stiffness is reversible.
Fractions of a water insoluble α-(1→3)-D-glucan (GL) extracted from Ganoderma lucidum were carboxy-methylated (CM) to obtain water-soluble carboxymethylated derivatives (CM-GL) having a degree of substitution (DS) of 0.38～0.51. Weight-average molecular weight Mw and intrinsic viscosity [η] of the samples CM-GL were measured by gelpermeation chromatography combined with laser light scattering (GPC-LLS) and viscometry. The CM-GL exhibits a stifferchain in aqueous solution at 25℃ than the original glucan. The antitumor activities against Ehrlich ascites carcinoma(EAC,5×106) of the carboxymethylated derivatives from the α-glucan and curdlan,a β-glucan,are significantly higher than those of the original glucans.The effects of the relatively low molecular weight,expanded chains and better water-solubility of the CMM-GL on the enhancement of antitumor activity could not be neglected.The chain stiffness decreased speedily with increase of temperature from 40 to 60℃ or NaOH concentration from 0.1 to 0.4 in the solution,respectively,and the change of the chain stiffness is reversible.
2001, 19(3): 291-296
Abstract:
A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used,the ratio of the acid mixture,the acid concentration,the ultrasonic agitation time and hydrolysis temperature.The number average molecular weight of NCC is determined by gel permeation chromatography (GPC).The particle size and shape were determined by transmission electron microscopy (TEM).X-ray diffraction was used to detect the crystallinity and average crystallite size of the particle.
A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used,the ratio of the acid mixture,the acid concentration,the ultrasonic agitation time and hydrolysis temperature.The number average molecular weight of NCC is determined by gel permeation chromatography (GPC).The particle size and shape were determined by transmission electron microscopy (TEM).X-ray diffraction was used to detect the crystallinity and average crystallite size of the particle.
2001, 19(3): 297-301
Abstract:
The morphological transition of molecular assemblies in aqueous solutions for a new amphiphilic diblockcopolymer induced by changing the initial solvent conditions was studied by transmission electron microscopy (TEM). Thecopolymer was polystyrene(77)-b-poly [2 -(β-D-glucopyranosyloxy) ethyl acrylate (6)] (PSt77-b-PGEA6) and the solvent was amixture of DMF and THF. PSt77-b-PGEA6 yields vesicles and tubules when it is initially dissolved in THF and DMF respectively. The morphological transition between vesicles and tubules can be achieved by simply varying the amounts of THF and DMF,or changing the temperature at which the aggregates were prepared.
The morphological transition of molecular assemblies in aqueous solutions for a new amphiphilic diblockcopolymer induced by changing the initial solvent conditions was studied by transmission electron microscopy (TEM). Thecopolymer was polystyrene(77)-b-poly [2 -(β-D-glucopyranosyloxy) ethyl acrylate (6)] (PSt77-b-PGEA6) and the solvent was amixture of DMF and THF. PSt77-b-PGEA6 yields vesicles and tubules when it is initially dissolved in THF and DMF respectively. The morphological transition between vesicles and tubules can be achieved by simply varying the amounts of THF and DMF,or changing the temperature at which the aggregates were prepared.
2001, 19(3): 303-309
Abstract:
Homogeneous polymerization of p-diethynylbenzene initiated by nickel acetylide Ni(C ≡ C C6H4 C ≡ CH)2(PPh3)2has been investigated in terms of different solvents, addition agents, atmosphere gases, catalyst concentrations, monomerconcentrations and polymerization temperatures. The yield and catalytic efficiency approach 88% and 11. 1 kg polymer/molNi, respectively, under the optimum conditions: [cat] = 0.01 mol/L, [M] = 1.0 mol/L, NEt3/cat (mol ratio) = 3～5, 1,4-dioxane/toluene (volume ratio) = 1 and T =25℃ for 5 h.The polymerization rate equation can be expressed as Rp=kp[M][cat]2, where kp=0.47 L2·mol-2·S-1(25℃).The overall polymerization activation energy was found to be 203 KJ·mol-.Poly(p-diethynylbenzene）so obtained is soluble in THF,CHCl3 and toluene with weight-average molecular weights as high as 27,100 and a rich-trans extended π-conjugated polyene chain structure with pendent groups of p-C6H4C=CH.
Homogeneous polymerization of p-diethynylbenzene initiated by nickel acetylide Ni(C ≡ C C6H4 C ≡ CH)2(PPh3)2has been investigated in terms of different solvents, addition agents, atmosphere gases, catalyst concentrations, monomerconcentrations and polymerization temperatures. The yield and catalytic efficiency approach 88% and 11. 1 kg polymer/molNi, respectively, under the optimum conditions: [cat] = 0.01 mol/L, [M] = 1.0 mol/L, NEt3/cat (mol ratio) = 3～5, 1,4-dioxane/toluene (volume ratio) = 1 and T =25℃ for 5 h.The polymerization rate equation can be expressed as Rp=kp[M][cat]2, where kp=0.47 L2·mol-2·S-1(25℃).The overall polymerization activation energy was found to be 203 KJ·mol-.Poly(p-diethynylbenzene）so obtained is soluble in THF,CHCl3 and toluene with weight-average molecular weights as high as 27,100 and a rich-trans extended π-conjugated polyene chain structure with pendent groups of p-C6H4C=CH.
2001, 19(3): 311-315
Abstract:
2-Hydroxycthyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electro-optical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser andscanning electron microscopy, respectively. With increasing E7 content in the copolymer, droplet size increased, thresholdvoltage decreased.
2-Hydroxycthyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electro-optical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser andscanning electron microscopy, respectively. With increasing E7 content in the copolymer, droplet size increased, thresholdvoltage decreased.
2001, 19(3): 317-322
Abstract:
Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer).The observation of spherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than those of β-PP homopolymer.
Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer).The observation of spherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than those of β-PP homopolymer.
