A NEURAL NETWORK STUDY ON GLASS TRANSITION TEMPERATURE OF POLYMERS

In this paper, an atificial neural network model is adopted to study the glass transition temperature of polymers. Inour artificial neural networks, the input nodes are the characteristic ratio C_∞, the average molecular weigh M_e betweenentanglement points and the molecular weigh M_(mon) of repeating unit. The output node is the glass transition temperature T_g,and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting theoutcome for polymers for which it is not trained. The maximum relative error for predicting of the glass transitiontemperature is 3.47%, and the overall average error is only 2.27%. Artificial neural networks may provide some new ideas toinvestigate other properties of the polymers.     

POLYMER CHAIN DIFFUSION AT A TEMPERATURE BELOW ITS BULK GLASS TRANSITION TEMPERATURE

In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in thebulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtainedresults clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristiclength scale of usual segmental motion even at a temperature below its bulk glass transition temperature, T_g~b. This isconsistent with our previous results that the surface glass transition temperature is much lower than the corresponding T_g~b.Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region.     

CORRELATION BETWEEN GLASS TRANSITION OF POLYMERS AND ENERGY OF ROTATIONAL ISOMERIZATION OF MOLECULAR CHAINS

It has been shown that the free volume fraction at T_g is not a universal parameter for linear polymers of different molecular structure. The reason is that the volume expansion at T_g is partially contributed from the change of the numbers of conformations of isolated molecular chains due to internal rotation. In this paper, glassy transformation was connected with internal rotation of isolated molecular chains, and the relationship between free volume fraction of polymers at T_g and energy e of rotational isomerization of isolated molecular chains was formulated, e=-k·T_g·In (△α·T_g/1-△α. T_g). The values of calculated from the above formula are in good agreement with those published in the literatures. Thus, the method described in this paper can be used to estimate a parameter for the flexibility of isolated molecular chains.7     

ON THE ORIGIN OF STRESS PEAK IN UNI-AXIAL STRETCHING OF AMORPHOUS POLYMERS

Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on theenineering stress-strain curve during stretching at room temperature. In this work cis-polybutadiene samples were swollen in a poor solvent, CHCl_3/EtOH (1/1 v/v), for differenttimes. It was found that both the initial modulus and the stress peak on stretching de-creased in magnitude with increasing swelling time and the peak disappeared entirely after1 hour of swelling. On further swelling the initial modulus increased somewhat and a smallstress peak re-appeared after swelling for 2 h. The disappearance of the stress peak afterswelling is interpreted as the result of disruption of cohesional entanglements present in theinitial rubber sample. The re-appearance of a small stress peak and the increase of modu-lus on further swelling are interpreted as being of the same nature as the phenomenon ofanti-plasticization. It is the result of forming some new cohesional entanglements of largerbinding energies through longer range chain segmental motions excited after the disruptionof the previously existing cohesional entanglements in the rubber. Thus an understand-ing of the stress peak on stretching a high molar mass rubber and the phenomenon ofanti-plasticization on molecular level has been put forward.     

A NOVEL SECOND-ORDER TRANSITION IN ORGANIC HYBRIDS CONSISTING OF POLYMERS AND SMALL MOLECULES

A novel transition appeared above thc glass transition temperature of chlorinated polyethylene (CPE) for binaryblends of CPE and additives such as organic small molecules or oligomers. This transition was assigned to the dissociation ofintermolecular hydrogen bonds between the polymer ard additive within the edditive rich phase. Of particular interest is thata novel pyramid crystal was observed in the annealed CPE/hindered phenol blends. Another intriguing observation is thatthese polymer/small molecule blends organized by intermolecular hydrogen bonding have several potential properties, suchas shape-memorization, self-restoration, self-adhesiveness and super damping.     

NUCLEATION ACTION OF THERMOTROPIC LIQUID CRYSTAL POLYMERS IN THE BLENDS WITH PET

The present work concerns the crystallization of PET accelerated by addition of thermotropic liquid crystalline polymers (TLCP)based on two aromatic copolyesters: PHB/PET (60:40 ) and PHB/HDA/2,6-DNA /IPA ( 50:25 : 12.5 : 12.5 ). The investigation has been made by measurements of the cold-crystallization and melt-crystallization temperatures by DSC and of the changes of density and depolarizing light intensity during the isothermal process. In addition, the morphology of selectively etched surface of compressing pellets proved the presence of crystalline fibrillar structure, it can be supposed to have grown up from the micelle nucleus based on bundle of rigid TLCP chains.     

VISCOMETRIC INVESTIGATIONS OF POLYVINYLPYRROLIDONE IN MIXED SOLVENTS AND WITH VARYING TEMPERATURE

The viscosity behavior of polyvinylpyrrolidone (PVP) has been determined at 25℃ in mixed solvents comprising water/dimethylformamide (DMF) and water /methanol (MeOH). Analysis of the data has considered the PVP as being both host and guest polymer in solution. The intrinsic viscosity of PVP in DMF is higher than in water and in MeOH, but also increases in a mixed solvent with high water content because of the effect of polymer-solvent interactions. It was also found that the intrinsic viscosity of PVP at finite concentration, [ηpvp]c decreases with an increase in the concentration of PVP in solution. The viscosity behavior of PVP in a mixed solvent is affected by the concentration-dependent intermolecular excluded volume effect, which can be quantitatively expressed by the parameter, bY, which reflects the shrinkage of PVP chain coils, resulting in a decrease of [ηpvp]c. The effect of temperature on the viscosity behavior of PVP in MeOH shows that the interaction parameter increases up to a maximum value, and then decreases after a certain temperature.     

FOURIER TRANSFORM INFRARED STUDIES OF POLY (ETHYLENE TEREPHTHALATE) FILM IN THE GLASS TRANSITION REGION

Three specimens from a solution-cast poly (ethylene terephthalate) (PET) film, one being liquid-N_2 quenched from 92℃(Q), one being slowly cooled from 92℃(SC) and one being quenched and sub-T_g annealed at 67℃(AN), have been studied by specimen difference spectra Q-SC and AN-Q and temperature difference spectra T-70 and T_2-T_1 for every 2℃steps on heating to 90℃at 2℃/min. SC and AN showed more gauche conformers than Q. That means that the PET chain has more trans conformers at higher temperatures and some of these are frozen during quenching through T_g. A band at 1340 cm~(-1) has been found to be complex containing overlapping bands reflecting trans in crystalline regions and trans in amorphous regions. The temperature difference spectra on heating through T_g showed that the spectral changes in Q are gradual while a rather abrupt change occurs in AN at 80—82℃for the bands at 1340, 1042 and 1020 cm~(-1). No new conformational structure or new vibrational mode is involved. A kind of locking mechanism is suggested which hinders the molecular vibrational changes in AN below T_g until a sudden release occurs at T_g. These locking sites can be nothing else than sites of tighter local packing of chain segments. Consequently it is believed that inter-chain van der Waals attraction energy plays a dominating role in the volume relaxation and sub-T_g annealing of quenched amorphous polymers.     

DETERMINATION OF PHOSPHORUS AND FLUORINE IN POLYMERS AND ORGANIC COMPOUNDS WITH Nd~(3+)

Percentages of P or/and F in polymers and organic compounds are found by using Nd~(3+) as pre-cipitant and subsequent titration of excess Nd~(3+) with EDTA after decomposing sample in oxygenflask. The errors of determination are for P<±0.20% and F<±0.30% except fully fluorinatedcompounds.     

THIN FILM ELECTRODES OF AMORPHOUS Ml－Ni ALLOY AS HYDROGEN CATHODES IN ALKALINE SOLUTION

ＴＨＩＮＦＩＬＭＥＬＥＣＴＲＯＤＥＳＯＦＡＭＯＲＰＨＯＵＳＭｌ－ＮｉＡＬＬＯＹＡＳＨＹＤＲＯＧＥＮＣＡＴＨＯＤＥＳＩＮＡＬＫＡＬＩＮＥＳＯＬＵＴＩＯＮ￥ＷｅｉＫａｎｇＨＵ；ＹｕｎＳｈｉＺＨＡＮＧａｎｄＹｕｎＷＡＮＧ（ＩｎｓｔｉｔｕｔｅｏｆＮｅｗＥｎｅ...     

MECHANICAL RELAXATION AND INTERMOLECULAR INTERACTION IN EPOXY RESINS/POLY (ETHYLENE OXIDE) BLENDS CURED WITH PHTHALIC ANHYDRIDE

The miscibility of the blend,composed of a bisphenol A epoxy resins (Diglycidyl etherof bisphenol A) (DGEBA) and poly(ethylene oxide) (PEO) and crosslinked by phthalicanhydride (PA) was studied using dynamic mechanical method. Single glass transitiontemperatures intermediate between the two pure components were observed for all blendlevels. The secondary relaxation mechanism should relate to not only diester linkage, butalso hydroxyether structural unit in the system. Fourier transform infrared spectroscopy(FTIR) is applied to study the curing reaction and intermolecular specific interaction of thesystem. The results indicate the PEO participates the crosslinking reaction, accelerates thecuring reaction and make the reaction more perfect. The shifts of the hydroxyl band andcarbonyl band demonstrate the presence of the intermolecular interaction in the curedblend. Moreover, the molecular interaction between the side hydroxyl in the hydroxyetherunits and the ether bond in PEO macromolecules is stronger.     

SYNTHESES OF Ph AND TEMPERATURE－SENSITIVE HYDROGELS AND THEIR APPLICATIONS IN CONTROLLED RELEASE OF BIOMACROMOLECULES

ＳＹＮＴＨＥＳＥＳＯＦＰｈＡＮＤＴＥＭＰＥＲＡＴＵＲＥ－ＳＥＮＳＩＴＩＶＥＨＹＤＲＯＧＥＬＳＡＮＤＴＨＥＩＲＡＰＰＬＩＣＡＴＩＯＮＳＩＮＣＯＮＴＲＯＬＬＥＤＲＥＬＥＡＳＥＯＦＢＩＯＭＡＣＲＯＭＯＬＥＣＵＬＥＳＦｅｎｇＬＩＵ；ＦｅｎｇＨｕａＬＩＵ；Ｇｕ...     

BAYER COUNTER CURRENT SYSTEMS IN COMPARISON WITH CONVENTIONAL CO－CURRENT SYSTEM IN THE FIELD OF WATER TREATMENT

ＢＡＹＥＲＣＯＵＮＴＥＲＣＵＲＲＥＮＴＳＹＳＴＥＭＳＩＮＣＯＭＰＡＲＩＳＯＮＷＩＴＨＣＯＮＶＥＮＴＩＯＮＡＬＣＯ－ＣＵＲＲＥＮＴＳＹＳＴＥＭＩＮＴＨＥＦＩＥＬＤＯＦ　ＷＡＴＥＲＴＲＥＡＴＭＥＮＴＭｉｔｓｃｈｋｅｒ．Ａ．ＲａｕｃｈｆｕＢ．Ｋ．，（Ｂａｙ...     

THE RELATIONSHIP BETWEEN RETENTION VALUES OF HOMOLOGUES AND THE COLUMN TEMPERATURE IN REVERSED－PHASE LIQUID CHROMATOGRAPHY

ＴＨＥ　ＲＥＬＡＴＩＯＮＳＨＩＰ　ＢＥＴＷＥＥＮ　ＲＥＴＥＮＴＩＯＮ　ＶＡＬＵＥＳ　ＯＦ　ＨＯＭＯＬＯＧＵＥＳ　ＡＮＤ　ＴＨＥ　ＣＯＬＵＭＮ　ＴＥＭＰＥＲＡＴＵＲＥ　ＩＮ　ＲＥＶＥＲＳＥＤ－ＰＨＡＳＥ　ＬＩＱＵＩＤ　ＣＨＲＯＭＡＴＯＧＲＡＰＨＹＴＨＥ...     

STUDIES OF FAR－INFRARED SPECTRA AND SOLID－SOLID PHASE TRANSITION IN ［n－C_nH_（2n＋1）NH_3］_2 CuX_4 LAYER COMPOUNDS WITH n＝7－12，16

ＳＴＵＤＩＥＳＯＦＦＡＲ－ＩＮＦＲＡＲＥＤＳＰＥＣＴＲＡＡＮＤＳＯＬＩＤ－ＳＯＬＩＤＰＨＡＳＥＴＲＡＮＳＩＴＩＯＮＩＮ［ｎ－Ｃ_ｎＨ_（２ｎ＋１）ＮＨ_３］_２ＣｕＸ_４ＬＡＹＥＲＣＯＭＰＯＵＮＤＳＷＩＴＨｎ＝７－１２，１６￥ＮｉｎｇＧＵＯ（Ｄｅｐａｒｔ?..     

DISTRIBUTIONS OF TEMPERATURE, VELOCITY AND VISCOSITY AT SYMMETRICAL AXIS OF CYLINDRICAL PLUME IN EARTH'S MANTLE WITH VARIABLE VISCOSITY

The parameters at the symmetrical axis of a cylindrical plume characterize the strength of this plume and provide a boundary condition which must be given to investigate the structure of a plume. For Newtonian fluid with a temperature-and pressure-dependence viscosity, an asymptotical solution of hydrodynamic equations at the symmetrical axis of the plume is found in the present paper. The temperature, upward velocity and viscosity at the symmetrical axis have been obtained as functions of depth, The calculated results have been given for two typical sets of Newtonian rheological parameters. The results obtained show that the temperature distribution along the symmetrical axis is nearly independent of the theological parameters. The upward velocity at the symmetrical axis, however, is strongly dependent on the rheological parameters.     

SYNTHESIS OF LINEAR POLYSILOXANE WITH PENDANT BENZO－15－C－5 MOIETIES AND ITS TRANPORT PROPERTIES IN BULK LIQUID MEMBRANE SYSTEM

ＳＹＮＴＨＥＳＩＳＯＦＬＩＮＥＡＲＰＯＬＹＳＩＬＯＸＡＮＥＷＩＴＨＰＥＮＤＡＮＴ　ＢＥＮＺＯ－１５－Ｃ－５ＭＯＩＥＴＩＥＳＡＮＤＩＴＳＴＲＡＮＰＯＲＴＰＲＯＰＥＲＴＩＥＳＩＮＢＵＬＫＬＩＱＵＩＤＭＥＭＢＲＡＮＥＳＹＳＴＥＭＣＨＥＮＹｕａｎｙｉｎ；Ｌｕ...     

A FACILE SYNTHESIS OF AZACROWN ETHERS WITH INTRAANNULAR PHENOLIC GROUPS IN A TWO－PHASE SYSTEM

ＡＦＡＣＩＬＥＳＹＮＴＨＥＳＩＳＯＦＡＺＡＣＲＯＷＮＥＴＨＥＲＳＷＩＴＨＩＮＴＲＡＡＮＮＵＬＡＲＰＨＥＮＯＬＩＣＧＲＯＵＰＳＩＮＡＴＷＯ－ＰＨＡＳＥＳＹＳＴＥＭ￥ＧｕｏＰｉｎｇＸＵＥ；ＣｈｅｎｇＴａｉＷＵ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，...     

FACILE AND SELECTIVE REDUCTION OF NTIROARENES IN THE PRESENCE OF NITRILES WITH NaBH_4－BiCl_3 SYSTEM

ＦＡＣＩＬＥＡＮＤＳＥＬＥＣＴＩＶＥＲＥＤＵＣＴＩＯＮＯＦＮＴＩＲＯＡＲＥＮＥＳＩＮＴＨＥＰＲＥＳＥＮＣＥＯＦＮＩＴＲＩＬＥＳＷＩＴＨＮａＢＨ_４－ＢｉＣｌ_３ＳＹＳＴＥＭ￥ＰｉｎｇＤａＲＥＮ，ＳｈｉＦｅｎｇＰＡＮ，ＴｉｎｇＷｅｉＤＯＮＧ，ＳｈｉＨｕｉ...     

THE STUDY ON ELECTROXIDATION OF Fe（CN）_6~（4－） WITH TIME－RESOLVED IN FRARED SPECTRA

ＴＨＥ　ＳＴＵＤＹ　ＯＮ　ＥＬＥＣＴＲＯＸＩＤＡＴＩＯＮ　ＯＦ　Ｆｅ（ＣＮ）＿６￣（４－）　ＷＩＴＨ　ＴＩＭＥ－ＲＥＳＯＬＶＥＤ　ＩＮ　ＦＲＡＲＥＤ　ＳＰＥＣＴＲＡ￥ＹｏｎｇＹＡＮＧ（ＳｔａｔｅＫｅｙＬａｂｏｒａｔｏｒｙｆｏｒＰｈｙｓｉｃａｌＣｈｅｍ...