Login In
1999 Volume 17 Issue 4
1999, 17(4): 309-314
Abstract:
The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observedby SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values atcritical crazing and yielding and the craze stability of PPQ-E samples depend on the thermal-dealingcondition for the samples. From the point of view of cohesional entanglements and energy absorbed bysamples, the experiment results were explained.
The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observedby SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values atcritical crazing and yielding and the craze stability of PPQ-E samples depend on the thermal-dealingcondition for the samples. From the point of view of cohesional entanglements and energy absorbed bysamples, the experiment results were explained.
1999, 17(4): 315-322
Abstract:
Molecular dynamics simulation of the relaxation at 300 K of a fully extended polyethylene chain of 800 CH2 units has been carried out by following the changes in morphology, van der Waals energy, radius ofgyration in the sense of mechanics and gyration radius in the sense of Flory, population of trans-conformation and orientation factor. The relaxation went through three stages: (1) relaxation from themorphology of a straight rod of 100 nm length to the molphology close to a random coil of gyration radius 5.9nm in 110 ps;(2)collapse of the morphology of a coil to a highly compact globule close to a sphere of gyration radius 1.3 nm after 178 ps as the result of intersegmental van der Waals attractive interactions;(3)lateral ordering of the folded chain segments in the globule without appreciable changes in the chain dimension up to 1600 ps,the time limit of present simulation.Nearly complete relaxation of local segmental orientation was performed much faster than the relaxation of globule chain orientation even for a single chain of low degree of polymerization and at a temperature some 155℃ above its Tg.The lateral ordering of the chain segments during the period 1778 to 680 ps of the simulation time was found to obey the Avrami equation with an Avrami index of 1.44.
Molecular dynamics simulation of the relaxation at 300 K of a fully extended polyethylene chain of 800 CH2 units has been carried out by following the changes in morphology, van der Waals energy, radius ofgyration in the sense of mechanics and gyration radius in the sense of Flory, population of trans-conformation and orientation factor. The relaxation went through three stages: (1) relaxation from themorphology of a straight rod of 100 nm length to the molphology close to a random coil of gyration radius 5.9nm in 110 ps;(2)collapse of the morphology of a coil to a highly compact globule close to a sphere of gyration radius 1.3 nm after 178 ps as the result of intersegmental van der Waals attractive interactions;(3)lateral ordering of the folded chain segments in the globule without appreciable changes in the chain dimension up to 1600 ps,the time limit of present simulation.Nearly complete relaxation of local segmental orientation was performed much faster than the relaxation of globule chain orientation even for a single chain of low degree of polymerization and at a temperature some 155℃ above its Tg.The lateral ordering of the chain segments during the period 1778 to 680 ps of the simulation time was found to obey the Avrami equation with an Avrami index of 1.44.
1999, 17(4): 323-328
Abstract:
Critical association concentration (CA) of ethylene-vinyl acetate copolymer (EVA) in selectivesolvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent)was investigated. DCE is a good solvent for polyvinyl acctate (PVAc) and a poor solvent for paraffin,whereas CYH is a good solvent for the paraffin and a precipitant for PVAc. Viscosities of EVA in differentcompositions of the solvent mixture with and without additives were measured. Viscosity results were used to detemine the CA value of the systems.It is shown that CA was markedly dependent on the composition of the solvent mixture and concentration and structure of additive.Solvation and competition between hydrogen bonding and micellisation were suggested for qualitative description of the changing of CA value observed.
Critical association concentration (CA) of ethylene-vinyl acetate copolymer (EVA) in selectivesolvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent)was investigated. DCE is a good solvent for polyvinyl acctate (PVAc) and a poor solvent for paraffin,whereas CYH is a good solvent for the paraffin and a precipitant for PVAc. Viscosities of EVA in differentcompositions of the solvent mixture with and without additives were measured. Viscosity results were used to detemine the CA value of the systems.It is shown that CA was markedly dependent on the composition of the solvent mixture and concentration and structure of additive.Solvation and competition between hydrogen bonding and micellisation were suggested for qualitative description of the changing of CA value observed.
1999, 17(4): 329-335
Abstract:
Two kinds of heterojunction diodes of porous silicon (PS) with soluble polyaniline (PANI) werefabricated. One is a heterojunction diode of PS with water-soluble copolymer of polyaniline (PAOABSA),Al/PS-PAOABSA/Au cell as rectifying diode. Another is a heterojunction diode of PS with solublepolyaniline doped with DBSA, Al/PS-PANI (DBSA)/Au cell as light emitting diode (LED). The rectifyingcharacteristics of the rectifying diodes were measured as a function of the degree of sulfonation and thickness of the copolymers,as well as oxidation of PS.The rectifying ratio of the heterojunction can reach 5.0×104 at ± 3 V bias.For the LED,the photoluminescence(PL) and electroluminescence(EL) spectra were measured and discussed.
Two kinds of heterojunction diodes of porous silicon (PS) with soluble polyaniline (PANI) werefabricated. One is a heterojunction diode of PS with water-soluble copolymer of polyaniline (PAOABSA),Al/PS-PAOABSA/Au cell as rectifying diode. Another is a heterojunction diode of PS with solublepolyaniline doped with DBSA, Al/PS-PANI (DBSA)/Au cell as light emitting diode (LED). The rectifyingcharacteristics of the rectifying diodes were measured as a function of the degree of sulfonation and thickness of the copolymers,as well as oxidation of PS.The rectifying ratio of the heterojunction can reach 5.0×104 at ± 3 V bias.For the LED,the photoluminescence(PL) and electroluminescence(EL) spectra were measured and discussed.
1999, 17(4): 337-342
Abstract:
Organic electroluminescent diodes with a heterostructure of 9,10-bis(phenylethnyl) anthracene(BPEA) doped poly(N-vinylcarbazole) (PVK)/tris(8-hydroxyquinoline)aluminum (Alq3) have beenfabricated. The electroluminescence (EL) both from BPEA and Alq3 were observed when the Alq3 layer isthin enough. With increasing thickness of the Alq3 layer, the relative emission intensity of BPEA is graduallydecreased. For the thin Alq3 layer structure, the light emission of Alq3 becomes more dominant as the applied voltage increases.It is proposed that the electron-hole recombination takes place in both PVK and Alq3 films.The field-induced quenching theory has also been applied to explain the change of the EL spectra with applied voltage.
Organic electroluminescent diodes with a heterostructure of 9,10-bis(phenylethnyl) anthracene(BPEA) doped poly(N-vinylcarbazole) (PVK)/tris(8-hydroxyquinoline)aluminum (Alq3) have beenfabricated. The electroluminescence (EL) both from BPEA and Alq3 were observed when the Alq3 layer isthin enough. With increasing thickness of the Alq3 layer, the relative emission intensity of BPEA is graduallydecreased. For the thin Alq3 layer structure, the light emission of Alq3 becomes more dominant as the applied voltage increases.It is proposed that the electron-hole recombination takes place in both PVK and Alq3 films.The field-induced quenching theory has also been applied to explain the change of the EL spectra with applied voltage.
1999, 17(4): 343-346
Abstract:
A blue dye, l-benzothiazoly-3-phenyl-pyrazoline (BTPP) was found to function as bright lightemitting dye in organic electroluminescent devices. This heterocyclic compound exhibits good characteristicsof blue photoluminescence and electroluminescence, which has emission peak at 445 nm.The thin films offluorescent dye dispersed in poly(N-vinylcarbazole) (PVK) could serve as light-emitting layers in multilayerorganic LEDs. 2-(4-Biphenyl)-5-(4-tert-butylpheynyl)-1,3,4-oxadiazole (PBD) and tris-(8-hydroxyquinoline)aluminum(Alq3)were introduced into double-layer and three-layer devices respectively.The introduction of electron transport material Alq3 enhanced the electron injection and luminous efficiency,as compared with double-layer devices.Maximum brightness and luminous efficiency can be reached up to 190 cd/m2 and 0.31m/W,respectively.
A blue dye, l-benzothiazoly-3-phenyl-pyrazoline (BTPP) was found to function as bright lightemitting dye in organic electroluminescent devices. This heterocyclic compound exhibits good characteristicsof blue photoluminescence and electroluminescence, which has emission peak at 445 nm.The thin films offluorescent dye dispersed in poly(N-vinylcarbazole) (PVK) could serve as light-emitting layers in multilayerorganic LEDs. 2-(4-Biphenyl)-5-(4-tert-butylpheynyl)-1,3,4-oxadiazole (PBD) and tris-(8-hydroxyquinoline)aluminum(Alq3)were introduced into double-layer and three-layer devices respectively.The introduction of electron transport material Alq3 enhanced the electron injection and luminous efficiency,as compared with double-layer devices.Maximum brightness and luminous efficiency can be reached up to 190 cd/m2 and 0.31m/W,respectively.
1999, 17(4): 347-354
Abstract:
The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains aredirectly obtained from a priori probability Pαβ. Here the differing statistical weight matrices for the Si-Oand O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, asthe same statistical weight matrices for the Si -O and O- Si bonds are adopted, there exists a large deviationof α priori probability Pαβ between the theory and the molecular dynamics (MD) simulation. Our model gives satisfactory agreement with experiment on the mean-square unperturbed end-to-end distance,the mean-square dipole moment and its temperature dependence,and the molar cyclization equilibrium constants for dimethylsiloxane oligomers.This new rotational isomeric state approach can be widely applied to other chains,such as —CH2—C[(CH2)mH]2—and —O—Si(CH2)mH]2 for arbitrary m.
The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains aredirectly obtained from a priori probability Pαβ. Here the differing statistical weight matrices for the Si-Oand O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, asthe same statistical weight matrices for the Si -O and O- Si bonds are adopted, there exists a large deviationof α priori probability Pαβ between the theory and the molecular dynamics (MD) simulation. Our model gives satisfactory agreement with experiment on the mean-square unperturbed end-to-end distance,the mean-square dipole moment and its temperature dependence,and the molar cyclization equilibrium constants for dimethylsiloxane oligomers.This new rotational isomeric state approach can be widely applied to other chains,such as —CH2—C[(CH2)mH]2—and —O—Si(CH2)mH]2 for arbitrary m.
1999, 17(4): 355-358
Abstract:
The synthesis, characterization and electroluminescence performance of a new type of conjugatedpolymer, poly(2,5-diphenyl-1,3,4-thiadiazolyl)-4,4'-vinylene (TPPV) are presented. A light-emitting diodeconsisted of ITO/TPPV/Al is driven at about 4.0 V and has a peak emission wavelength of 485 nm. Thisblue-shift of the peak is due to the decrease of conjugate degree of TPPV compared to PPV. This result is inaccord with that determined by XPS and theoretical model of MNDO/3
The synthesis, characterization and electroluminescence performance of a new type of conjugatedpolymer, poly(2,5-diphenyl-1,3,4-thiadiazolyl)-4,4'-vinylene (TPPV) are presented. A light-emitting diodeconsisted of ITO/TPPV/Al is driven at about 4.0 V and has a peak emission wavelength of 485 nm. Thisblue-shift of the peak is due to the decrease of conjugate degree of TPPV compared to PPV. This result is inaccord with that determined by XPS and theoretical model of MNDO/3
1999, 17(4): 359-365
Abstract:
A novel monomer, (trans)-7-[4-N,N-(di-β-hydroxyethyl) amino-benzene]-ethenyl-3,5-dinitro-thiophene (HBDT), was synthesized and characterized. The details of synthesizing the monomer andprepolymer, polyurethane with the monomer covalently incorporated are presented. The prepolymer andpolyurethane exhibited good solubility in common organic solvents. Molecular nonlinear optical properties ofthe monomer (HBDT) substituted thiophene based stilbenes is presented.
A novel monomer, (trans)-7-[4-N,N-(di-β-hydroxyethyl) amino-benzene]-ethenyl-3,5-dinitro-thiophene (HBDT), was synthesized and characterized. The details of synthesizing the monomer andprepolymer, polyurethane with the monomer covalently incorporated are presented. The prepolymer andpolyurethane exhibited good solubility in common organic solvents. Molecular nonlinear optical properties ofthe monomer (HBDT) substituted thiophene based stilbenes is presented.
1999, 17(4): 367-370
Abstract:
It has been an established practice to estimate the Θ-temperature of a polymer solution from thedisappearance of the interchain interactions (A2 = 0) Recently, in studies of the temperature dependence ofthe chain conformation in solution, we found that the change of the chain conformation clearly underwentthree different stages which could be viewed as the "gas". "liquid" and "solid" states in terms of the freedomof the "blobs" on the chain. The transition temperature between the first and second stages corresponds nicely to the Θ-temperature determined by the conventional method.It reveals,for the first time,that the Θ-temperature can be deduced from the conformation change of a single polymer chain in solution,which is important not only in conception,but also in practice.
It has been an established practice to estimate the Θ-temperature of a polymer solution from thedisappearance of the interchain interactions (A2 = 0) Recently, in studies of the temperature dependence ofthe chain conformation in solution, we found that the change of the chain conformation clearly underwentthree different stages which could be viewed as the "gas". "liquid" and "solid" states in terms of the freedomof the "blobs" on the chain. The transition temperature between the first and second stages corresponds nicely to the Θ-temperature determined by the conventional method.It reveals,for the first time,that the Θ-temperature can be deduced from the conformation change of a single polymer chain in solution,which is important not only in conception,but also in practice.
1999, 17(4): 371-373
Abstract:
Optically active polyurethane was synthesized by the polyaddition of (2R, 3R)-(+)-diethyl L-tartrate (DET), 4,4'-diphenylmethane diisocyanate (MDI) and polyethylene glycol (PEG) with variousmolecular weights at 60℃ in DMSO. The polymers were characterized by specific rotation, DSC and 1HNMR spectra.
Optically active polyurethane was synthesized by the polyaddition of (2R, 3R)-(+)-diethyl L-tartrate (DET), 4,4'-diphenylmethane diisocyanate (MDI) and polyethylene glycol (PEG) with variousmolecular weights at 60℃ in DMSO. The polymers were characterized by specific rotation, DSC and 1HNMR spectra.
1999, 17(4): 375-378
Abstract:
The morphological features of a side-chain liquid crystalline polymer during the mesophasetransitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogensof three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture wasobserved in the transition temperature range. Similar to main-chain liquid crystalline polymers the transitionprocess of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local olaces of the old phase matrix and a growth process of the new phase domains.
The morphological features of a side-chain liquid crystalline polymer during the mesophasetransitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogensof three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture wasobserved in the transition temperature range. Similar to main-chain liquid crystalline polymers the transitionprocess of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local olaces of the old phase matrix and a growth process of the new phase domains.
1999, 17(4): 379-382
Abstract:
1, 1,4,4-Tetraphenyl-1,3-butadiene (TPB) was successfully introduced into the polymer multilayerfilms by means of Langmuir-Blodgett (LB) technique. Results of UV-VIS spectra and X-ray diffractionshowed that the uniform films had a layer structure similar to the superlattice of organic multiple quantumwells. The electroluminescence (EL) devices fabricated from the doped polymer LB films emitted blue light.Compared with the casting films, the photoluminescence (PL) and EL spectra showed that the exciton energy shifts to higher and the half-width of the emission peak becomes narrower due to exciton eoncinement effect.
1, 1,4,4-Tetraphenyl-1,3-butadiene (TPB) was successfully introduced into the polymer multilayerfilms by means of Langmuir-Blodgett (LB) technique. Results of UV-VIS spectra and X-ray diffractionshowed that the uniform films had a layer structure similar to the superlattice of organic multiple quantumwells. The electroluminescence (EL) devices fabricated from the doped polymer LB films emitted blue light.Compared with the casting films, the photoluminescence (PL) and EL spectra showed that the exciton energy shifts to higher and the half-width of the emission peak becomes narrower due to exciton eoncinement effect.
1999, 17(4): 383-389
Abstract:
Fluorescent molecules - p-dimethylaminobenzonitrile (DMABN) and trans-stilbene (TSB) -were used as probes to investigate the inner structure of the nanotubular cavities contained in a newpolyorganosiloxane (POS) which was prepared by the hydrosilylation coupling reaction of cis-isotacticladderlike polyvinylsilsesquioxane (Vi-T) with 1, 1,3,3-tetramethyldisiloxane (H-MM) as coupling agent inthe presence of catalyst dicyclopentadienyldichloroplatin (Cp2PtCl2). The results from FTIR spectra and fluorescence spectra in combination with molecular simulation reveal that the cross-section of the nanotubular cavity is nearly rectangular in shape,and is about 0.62 nm in width and about 0.38 nm in height.This work gains in-depth knowledge into the inner structure of the nanotubular cavities of POS and furthermore provides a guide to the selection of proper guest molecules in constructing functional supramolecular clathrate based upon POS.
Fluorescent molecules - p-dimethylaminobenzonitrile (DMABN) and trans-stilbene (TSB) -were used as probes to investigate the inner structure of the nanotubular cavities contained in a newpolyorganosiloxane (POS) which was prepared by the hydrosilylation coupling reaction of cis-isotacticladderlike polyvinylsilsesquioxane (Vi-T) with 1, 1,3,3-tetramethyldisiloxane (H-MM) as coupling agent inthe presence of catalyst dicyclopentadienyldichloroplatin (Cp2PtCl2). The results from FTIR spectra and fluorescence spectra in combination with molecular simulation reveal that the cross-section of the nanotubular cavity is nearly rectangular in shape,and is about 0.62 nm in width and about 0.38 nm in height.This work gains in-depth knowledge into the inner structure of the nanotubular cavities of POS and furthermore provides a guide to the selection of proper guest molecules in constructing functional supramolecular clathrate based upon POS.
1999, 17(4): 391-395
Abstract:
While WCl6-Ph4Sn fails to polymerize 1-phenyl-1-propyne (PP) at room temperature, highmolecular weight (Mw up to 410× 103) polymers are obtained in high yields (up to 80%) when thepolymerizations of PP are carried out in the presence of C60 using the W catalyst under the same conditions.The polymers are soluble in common organic solvents such as THF, chloroform, and toluene. Molecularstructures of the polymers are characterized by FT-IR, UV, NMR, GPC and XRD, and it is found that C60 is copolymerized with PP.Thus C60 plays the dual roles of comonomer and cocatalyst in the porymerization reaction.C60 contents of the copolymers can be easily changed by varying the C60 amounts in the feed mixtures.The copolymers effectively limit strong 532 nm laser pulses,whose limiting performance is superior to that of parent C60.
While WCl6-Ph4Sn fails to polymerize 1-phenyl-1-propyne (PP) at room temperature, highmolecular weight (Mw up to 410× 103) polymers are obtained in high yields (up to 80%) when thepolymerizations of PP are carried out in the presence of C60 using the W catalyst under the same conditions.The polymers are soluble in common organic solvents such as THF, chloroform, and toluene. Molecularstructures of the polymers are characterized by FT-IR, UV, NMR, GPC and XRD, and it is found that C60 is copolymerized with PP.Thus C60 plays the dual roles of comonomer and cocatalyst in the porymerization reaction.C60 contents of the copolymers can be easily changed by varying the C60 amounts in the feed mixtures.The copolymers effectively limit strong 532 nm laser pulses,whose limiting performance is superior to that of parent C60.
1999, 17(4): 397-402
Abstract:
Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in thisinvestigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied usingTaCl5, NbCl5, Mo(CO)4(nbd) and [Mo(CO)3cp]2 as catalysts (where nbd = 2,5-norbornadiene, cp = cyclo-pentadiene). A soluble polymer was obtained when the polymerization of 1.9-decadiyne was initiated byTaCl5 at low temperature (0℃). The polymer, however, became partially soluble after purification, possibly due to the postpolymerization-induced crosslinking.NbCl5-catalyzed polymerization of 1,9-bis(trimethylsilyl)-1,-8-nonadiyne gave a completely soluble polymer.Soluble polymers were also obtained from the polymerization of 3,9-dodecadiyne initiated by NbCl5,Mo(CO)4(nbd),[Mo(CO)3cp]2,PdCl2-ClSiMe3 and Pd/C-ClSiMe3.IR,UV,and NMR spectroscopic analysis revealed that different catalysts gave polymers with different structures,ranging from linear polyenes to hyperbranched polyphenylenes.The polymers absorb UV light at around 250 nm and emit fluorescence at 340 nm when they are excited at 248 nm.
Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in thisinvestigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied usingTaCl5, NbCl5, Mo(CO)4(nbd) and [Mo(CO)3cp]2 as catalysts (where nbd = 2,5-norbornadiene, cp = cyclo-pentadiene). A soluble polymer was obtained when the polymerization of 1.9-decadiyne was initiated byTaCl5 at low temperature (0℃). The polymer, however, became partially soluble after purification, possibly due to the postpolymerization-induced crosslinking.NbCl5-catalyzed polymerization of 1,9-bis(trimethylsilyl)-1,-8-nonadiyne gave a completely soluble polymer.Soluble polymers were also obtained from the polymerization of 3,9-dodecadiyne initiated by NbCl5,Mo(CO)4(nbd),[Mo(CO)3cp]2,PdCl2-ClSiMe3 and Pd/C-ClSiMe3.IR,UV,and NMR spectroscopic analysis revealed that different catalysts gave polymers with different structures,ranging from linear polyenes to hyperbranched polyphenylenes.The polymers absorb UV light at around 250 nm and emit fluorescence at 340 nm when they are excited at 248 nm.
