@article { ISI:000233391900008, title = {Design, syntheses, and characterization of new thermoplastic polyureas based on 3,4-ethylenedioxythiophene}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {43}, number = {23}, year = {2005}, month = {DEC}, pages = {5823-5830}, publisher = {WILEY-BLACKWELL}, type = {Article}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

New thermoplastic polyureas labeled PUn (n = 2, 3, 4, 6, 7, 9, or 10), based on 3,4-ethylenedioxythiophene (EDOT) with flexible aliphatic spacers, were synthesized and characterized for the first time. EDOT was chosen as a replacement for the aromatic phenyl group in conventional thermoplastics based on urea linkages to improve solubility without compromising the thermal properties. As synthesized, all the samples exhibited a semicrystalline nature. The glass-transition and melting temperatures showed a strong dependence on the spacer length. A comparison of the thermal properties of these polyureas with the corresponding phenyl analogues indicated that EDOT was a viable heteroatomic analogue of the phenyl group to be inserted into the main-chain polyureas without hampering their thermal stability. The polyureas with spacer lengths greater than hexamethylene formed transparent gels in N-methylpyrrolidone, 1,1,2,2-tetrachloroethane, and dimethyl sulfoxide. The molecular packing of the polyureas was assigned with wide-angle X-ray diffraction studies. (c) 2005 Wiley Periodicals, Inc.

}, keywords = {3, 4-ethylenedioxythiophene, heteroaromatic polymers, Polyurea, polyurea gels, Thermogravimetric analysis (TGA), thermoplastics, WAXS}, issn = {0887-624X}, doi = {10.1002/pola.21065}, author = {Ojha, U. P. and Ramesh, C. and Kumar, Anil} } @article { ISI:000229181600012, title = {Effect of connectivity and terminal functionality on mesophase behaviour of thermotropic liquid crystals containing biphenyl units}, journal = {Liquid Crystals}, volume = {32}, number = {4}, year = {2005}, month = {APR}, pages = {499-512}, publisher = {TAYLOR \& FRANCIS LTD}, type = {Article}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

A series of 4,4{\textquoteright}-disubstituted biphenyls, designated as series HBC, in which, one substituent is an ester group linked directly to the ring and the other is the hydroxy-containing group O(CH2)(n)OH, have been prepared and analysed by differential scanning Calorimetry, polarizing optical microscopy and X-ray diffraction. The introduction of a trimethylene unit between the ester functional group and the biphenyl moiety of the HBC series gives rise to the HBB series, which did not exhibit liquid crystalline behaviour. Interestingly, mesophase behaviour could be restored by replacing the methylene group ( of the trimethylene unit) that was directly attached to the biphenyl ring by a keto group (HBOB series). When the terminal hydroxy group of these three series was substituted by a group such as acetoxy or hydrogen, the transition temperatures were reduced, and the disappearance of mesophase behaviour was observed in some cases. However, this could be recovered by the replacement of the ester group by a carboxylic acid group.

}, issn = {0267-8292}, doi = {10.1080/02678290500033802}, author = {Ranganathan, T. and Ramesh, C. and Kumar, Anil} } @article { ISI:000228499400014, title = {Main chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB-type self-polycondensation route: FT-IR and XRD studies}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {43}, number = {9}, year = {2005}, month = {MAY}, pages = {1903-1912}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

The detailed mesophasic characterization of main chain liquid crystalline polyurethanes containing biphenyl mesogen, which were synthesized by the novel AB-type self-polycondensation approach, was carried out by using Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM), variable temperature X-ray Diffraction (XRD), and Fourier Transform Infrared (FT-IR) spectroscopic studies. The type of mesophase present in these polymers was identified to be the smectic A phase by POM and XRD studies. The smectic layer thickness was found to increase as the length of the spacer increased. The effect of temperature on the hydrogen bonding was analyzed by FT-IR studies. The curve-fitting analysis of the NH stretching and C=O stretching modes of vibrations indicated a gradual decrease in hydrogen bonding during the transition from the crystalline state to the mesophase. The mesophase to isotropic liquid transition was then accompanied by the complete disappearance of the hydrogen bonding. The biphenyl bands also showed changes during phase transitions due to the coupling of biphenyl vibration modes with the urethane linkage attached to it. (c) 2005 Wiley Periodicals, Inc.

}, keywords = {FT-IR, liquid-crystalline polymers, polyurethanes, XRD studies}, issn = {0887-624X}, doi = {10.1002/pola.20668}, author = {Ranganathan, T. and Gowd, E. B. and Ramesh, C. and Kumar, Anil} } @article { ISI:000226466700032, title = {Studies on the crystallization behavior of nylon-6 in the presence of layered silicates using variable temperature WAXS and FTIR}, journal = {Macromolecules}, volume = {38}, number = {2}, year = {2005}, month = {JAN}, pages = {454-462}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The crystallization of nylon-6 clay nanocomposite was studied by variable temperature wide-angle X-ray scattering (WAXS) and Fourier transform infrared spectroscopy (FTIR). Nylon-6 was found to crystallize into gamma phase at 210 degreesC, as indicated by its characteristic peaks in WAXS. However, an additional peak was observed close but on the lower angle side of the main gamma phase peak, indicating the presence of a metastable phase. The extent of metastable phase that developed was dictated by the clay content in the nanocomposite as well as the crystallization conditions. The temperature dependence of the d spacing of the gamma phase obtained in the presence of clay layers showed difference from the gamma phase obtained by treating nylon-6 in KI/I-2 solution. Variable temperature FTIR studies were conducted on the gamma phases for the first time, and it showed definite differences in the spectra of the phases obtained by the two methods.

}, issn = {0024-9297}, doi = {10.1021/ma048860d}, author = {Nair, S. S. and Ramesh, C.} } @article { ISI:000236996200020, title = {Crystalline phases in nylon-11: studies using HTWAXS and HTFTIR}, journal = {Macromolecules}, volume = {39}, number = {8}, year = {2006}, month = {APR}, pages = {2841-2848}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nylon-11 was crystallized into different crystalline phases by appropriate methods. The chance in the structure during heating was monitored in situ by wide-angle X-ray scattering (WAXS). The alpha phase obtained by precipitating nylon-11 in 1,4-butanediol started transforming into the pseudohexagonal phase on heating, but the transformation was not fully completed before melting. The melt crystallized sample at 175 degrees C gave the pseudohexagonal phase, which transformed into the alpha{\textquoteright} phase on cooling to room temperature at about 100 degrees C. The d spacing of the 00 1 reflection also showed a change at the transition temperature. The melt-quenched sample showed the pseudohexagonal phase, which did not change during heating, but on cooling transformed into alpha{\textquoteright} phase. The gamma phase was obtained by casting nylon-11 in trifluoroacetic acid (TFA), and it changed into the pscudohexagonal phase at about 110 degrees C on heating. The d spacing of the 001 reflection depended on the way in which it was obtained. The studies have shown that nylon-11 is one of the few nylons that exhibit an extensive degree of polymorphism. High-temperature Fourier transform infrared spectroscopy (HTFTIR) studies revealed, apart from the conformational differences between various phases of nylon-11, some information on the formation of the gamma phase.

}, issn = {0024-9297}, doi = {10.1021/ma052597e}, author = {Nair, S. S. and Ramesh, C. and Tashiro, K.} } @article { ISI:000241106900008, title = {Preparation and characterization of sulfonated syndiotactic polystyrene ionomers/organoclay nanocomposites}, journal = {Macromolecules}, volume = {39}, number = {21}, year = {2006}, month = {OCT}, pages = {7199-7203}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, issn = {0024-9297}, doi = {10.1021/ma061471u}, author = {Govindaiah, P. and Mallikarjuna, S. R. and Ramesh, C.} } @article { ISI:000241686000001, title = {Synthesis and characterization of main chain thermotropic liquid crystalline polyesters based on methyl 4-[4 {\textquoteleft}-(omega-hydroxyalkoxy)blphenyl-4-yl]-4-oxobutyrate: Effects of keto group and connectivity on mesophasic characteristics of biphenyl based AB-typ}, journal = {Reactive \& Functional Polymers}, volume = {66}, number = {10}, year = {2006}, month = {OCT}, pages = {1003-1013}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A series of biphenyl based main chain thermotropic liquid crystalline polyesters, poly(hydroxyalkoxybiphenyl oxobutyrate) [PRBOB-2,n (n = 2-8)], containing various methylene spacers was synthesized by using the novel AB-type self-polycondensation route from the monomers, methyl 4-[4{\textquoteright}-(omega-hydroxyalkoxy)biphenyl-4-yl]-4-oxobutyrate (HBOB-2,n). The mesophase characteristics of these polyesters was studied using DSC, polarized light optical microscopy and XRD techniques. The transition temperatures were found to decrease upon increasing the spacer length with an even polymer exhibiting higher transition temperature than the odd counterpart. The mesophase type also indicated an odd-even oscillation with the even members showing normal smectic phase and odd members exhibiting tilted smectic phase. The comparison of mesophasic characteristics of these polyesters with that of structurally similar AB-type polyesters indicated that the total number of atoms connecting the mesogen in a polymeric repeat unit governs the nature of the mesophase while the rigidity of the system dictates the magnitude of transition temperatures. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {AB approach, biphenyl mesogen, effect of connectivity, Liquid crystalline polyesters}, issn = {1381-5148}, doi = {10.1016/j.reactfunctpolym.2006.01.019}, author = {Ranganathan, T. and Ramesh, C.} } @article { ISI:000249395500018, title = {Copolyesters based on poly(butylene terephthalate)s containing cyclohexyl and cyclopentyl ring: Effect of molecular structure on thermal and crystallization behavior}, journal = {Macromolecules}, volume = {40}, number = {19}, year = {2007}, month = {SEP}, pages = {6906-6915}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

In an effort to understand the role of molecular structure on the thermal properties of polyesters and copolyesters, the following polyesters were synthesized: poly(1,4-cyclohexane dimethylene terephthalate) (PCT), poly(butylene-1,4-cyclohexane dicarboxylate) (PBCD), poly (1,3-cyclopentane dimethylene terephthalate) (PCPDT), and poly(butylene-1,3-cyclopentane dicarboxylate) (PBCP). PCT and PCPDT are semicrystalline polymers with crystallization and melting temperatures higher than poly(butylene terephthalate) (PBT). However, PBCD and PBCP have lower glass transition temperature than PBT. From these homopolymers a series of poly(butylene-co-1,4-cyclohexane dimethylene terephthalate) (P(BT-co-CT )), poly(butylene terephthalate-co-1,4cyclohexane dicarboxylate) (P(BT-co-BCD)), poly(butylene-co-1,3-cyclopentylene dimethylene) (P(BT-co-CPDT)), and poly(butylene terephthalate-co-1,3-cyclopentane dicarboyxlate) (P(BT-co-PBCP)) random copolyesters were synthesized for the first time, and their cocrystallization behavior was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The copolymers were found to be statistically random and crystallized in all compositions. The P(BT-co-CT) and (P(BT-co-CPDT) copolyesters exhibited typical eutectic behavior in melting and crystallization, which indicated isodimorphic cocrystallization behavior. On the other hand, in the case of P(BT-co-BCD) and P(BT-co-PBCP) copolymers, the melting and crystallization temperatures showed linear dependency with composition, indicating isomorphic-like crystallization behavior.

}, issn = {0024-9297}, doi = {10.1021/ma071272q}, author = {Sandhya, T. E. and Ramesh, C. and Sivaram, S.} } @article { ISI:000261767400044, title = {Role of solvent molecules as a trigger for the crystal phase transition of syndiotactic polystyrene/solvent complex}, journal = {Macromolecules}, volume = {41}, number = {24}, year = {2008}, month = {DEC}, pages = {9814-9818}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The phase transitions occurring in the syndiotactic polystyrene-norbornadiene complex were investigated by simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). To understand the effect of norbornadiene molecules on the phase-transition behavior, the delta form samples with different contents of norbornadiene were prepared. By heating these samples, we found that the delta-to-gamma transition occurred well below 100 degrees C in a broad temperature range, and the onset of the transition temperature depended on the content of norbornadiene included in the starting sample. The sample without norbornadiene molecules showed the delta-to-gamma transition to be above 100 degrees C. Upon further heating, the gamma form transformed into a mixture of alpha and beta forms in the presence of norbornadiene molecules, whereas the sample without norbornadiene transformed into only the alpha form. In this way, it has been found that the solvent molecules, which are not completely evaporated from the sample but are transiently trapped in the amorphous region because of the slow diffusion, have a significant role in facilitating the phase transitions as well as the transition temperatures in the crystalline region. On the basis of WAXD and DSC results, a phase-transition model has been reasonably constructed.

}, issn = {0024-9297}, doi = {10.1021/ma801742p}, author = {Gowd, E. Bhoje and Tashiro, Kohji and Ramesh, C.} } @article { ISI:000264717200003, title = {Structural phase transitions of syndiotactic polystyrene}, journal = {Progress in Polymer Science}, volume = {34}, number = {3}, year = {2009}, month = {MAR}, pages = {280-315}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Syndiotactic polystyrene (sPS) exhibits four crystal modifications (alpha, beta, gamma, and delta), along with intermediate forms with different molecular conformations, as well as different chain-packing structures. The extensive literature on the crystal structures exhibited by sPS is reviewed herein, including, the mechanisms of phenomena such as solvent-induced crystallization, thermally induced crystallization and gelation, and the phase transitions among the various crystalline forms. The latter have been studied by static and dynamic wide-angle and small-angle X-ray scattering, infrared and Raman spectra, and neutron scattering, etc., in addition to computer simulations. (C) 2009 Elsevier Ltd. All rights reserved.

}, keywords = {crystal structure, Gelation, phase transition, polymorphism, Solvent-induced crystallization, Syndiotactic polystyrene}, issn = {0079-6700}, doi = {10.1016/j.progpolymsci.2008.11.002}, author = {Gowd, E. Bhoje and Tashiro, Kohji and Ramesh, C.} } @article { ISI:000312452700005, title = {Structure-property relationship of different types of polyester industrial yarns}, journal = {Journal of the Textile Institute}, volume = {104}, number = {1}, year = {2013}, month = {JAN}, pages = {35-45}, publisher = {TAYLOR \& FRANCIS LTD}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

Four major types of polyester industrial yarns (1000 Denier) which are used commercially were studied for their key structural parameters. An attempt has been made to establish a relationship between morphology and properties of these yarns. High tenacity (HT) polyester yarn has the highest birefringence, amorphous orientation, and long period but is relatively less crystalline. High shrinkage characteristic of HT polyester yarn can be accounted for its higher amorphous orientation. High modulus low shrinkage (HMLS) polyester yarn has higher crystallinity and crystal size compared to HT yarn. Fraction of tie molecules of these yarns has been calculated and found that low shrinkage (LS) and super low shrinkage (SLS) yarns have lesser tie molecules. These LS and SLS yarns are tailor-made to achieve lower shrinkage and at the same time maintaining a good level of tenacity. This is achieved with lower amorphous orientation in the final drawn yarn structure. Amorphous orientation was found to have stronger influence than any other structural parameter on the key yarn properties like modulus, tenacity, elongation, and shrinkage.

}, keywords = {modulus, orientation, polyester, shrinkage, structure}, issn = {0040-5000}, doi = {10.1080/00405000.2012.693277}, author = {Samui, Barun Kumar and Prakasan, Manikanda Priya and Ramesh, C. and Chakrabarty, Debabrata and Mukhopadhyay, R.} } @article { ISI:000380167200011, title = {Studies on the static and dynamic properties of different types of polyester industrial yarns}, journal = {Journal of the Textile Institute}, volume = {107}, number = {9}, year = {2016}, month = {OCT}, pages = {1175-1184}, publisher = {TAYLOR \& FRANCIS LTD}, address = {2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND}, abstract = {

Four major types of polyester industrial yarns, viz. high tenacity (HT), high modulus low shrinkage (HMLS), low shrinkage (LS) and super low shrinkage (SLS) polyester yarns, were studied for their static and dynamic properties. An attempt has been made to establish a linkage between static and dynamic properties of these yarns with its structure and with its end applications. HMLS and HT polyester yarns have lower tan delta and work loss, which are the desired characteristics required for its end applications which include tire and conveyer belt. Higher overall orientation and higher fraction of tie molecules helped to achieve these properties in HT and HMLS polyester yarns. LS and SLS polyester yarns are mostly used for static applications. Low thermal shrinkage is the key requirement for the downstream processes of these yarns. Lower amorphous orientation in these two yarns is primarily responsible for achieving very low thermal shrinkage. A good co-relation has been established between the peak temperature of work loss (in slow speed hysteresis test) and the peak temperature of tan delta (in high-speed dynamic test).

}, keywords = {creep, modulus, polyester, shrinkage, tan delta, work loss}, issn = {0040-5000}, doi = {10.1080/00405000.2015.1097087}, author = {Samui, Barun Kumar and Dasgupta, Saikat and Mukhopadhyay, R. and Ramesh, C. and Chakrabarty, Debabrata} } @article {45566, title = {Borassus powder-reinforced poly(lactic acid) composites with improved crystallization and mechanical properties}, journal = {Journal of Applied Polymer Science}, volume = {136}, year = {2019}, month = {JAN}, pages = {Article No: 47440}, type = {Article}, abstract = {This article reports on the development of biocomposites based on polylactic acid (PLA) and borassus powder. Borassus powder was treated with alkali to remove hemicelluloses and lignin. The treated borassus improved the homogeneous mixing with PLA and increased the crystallinity of PLA. Dispersibility of the borassus was studied by scanning electron microscopy (SEM) and X-ray MicroCT. PLA/borassus composites were prepared by melt mixing of PLA with 5, 10, and 15 wt \% treated/untreated borassus. Composites were examined for mechanical properties and crystallization. Composites showed enhanced tensile strength compared to neat PLA. The PLA/treated borassus powder composites displayed higher crystallinity than PLA. The isothermal cold crystallization study showed increase in the crystallization rate of PLA in the presence of treated borassus. The spherulitic growth was studied using polarized optical microscopy. The enhanced performance of the PLA-borassus composites was observed in the presence of borassus. This study demonstrates that the PLA-borassus composites show great promise for bioplastics applications.}, doi = {10.1002/app.47440}, author = {Marathe, Y. N. and Arun, Torris A. T. and Ramesh, C. and Badiger, M. V.} }