A kinked unit-containing thermotropic liquid crystalline copolyester with low glass transition temperature and broad phase transition temperature

2009 ◽  
Vol 47 (18) ◽  
pp. 4703-4709 ◽  
Author(s):  
Heng-Zhen Huang ◽  
Li Chen ◽  
Yu-Zhong Wang
Keyword(s):  
Phase Transition ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Phase Transition Temperature ◽  
Liquid Crystalline ◽  
Liquid Crystalline Copolyester

Phase transition in non-crystalline solids viewed from heating

1995 ◽  
Vol 398 ◽  
Author(s):  
K. Nakayama ◽  
K. Kojima ◽  
N. Takahashi ◽  
Y. Masaki ◽  
A. Kitagawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Heating Rate ◽  
Transient Phase ◽  
Disordered Structures ◽  
Fragmentation Processes ◽  
Scaling Rule

ABSTRACTThe heating-rate dependence of crystallization temperature, Tc, and the glass transition temperature, Tg, is studied from the view points of nucleation and fragmentation processes in disordered structures. Tc and Tg are expected to increase monotonically with heating rate. Such behaviors of Tc and Tg are classified into four characteristic regions with respect to the heating rate. Results are summarized in the Transient Phase Diagram where Tc and Tg are given as a function of heating rate. The scaling rule in the Transient Phase Diagram is given.

Preparation and characterization of post-derivatives from functional polystyrene (ATRP) with p-nitroanilineazomethine phenol and their thermal and optical study

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Xifei Yu ◽  
Guo Zhang ◽  
Tongfei Shi ◽  
P.K. Dutta ◽  
Lijia An
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Liquid Crystalline ◽  
Gel Permeation Chromatography ◽  
Side Chain ◽  
Scanning Calorimetry ◽  
Xrd Study ◽  
Covalently Linked

AbstractThe functional polystyrene, (Cl-PS)2-CHCOOCH2CH2OH (designated as XPSt and coded P2) was prepared by ATRP at 1300C using CuCl and bipyridine as catalysts, 2,2-dichloro acetate-ethylene glycol (DCAG) as multifunctional initiator and THF as solvent. 4-Nitoroaniline azomethine-4’ phenol (P1) as chromophores were covalently linked to the functional end groups of the polymer by using simple displacement reaction. The functional polystyrenes, namely XPSt (P2) and (PS)2-CHCOOCH2CH2OH, designated as X-PSt and coded P3 and their post-derivatives, namely, DXPSt (P4) and DX-PSt (P5) respectively were characterized by IR, NMR and UV spectroscopies, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), polarising optical microscopy (POM) and XRD studies. DSC showed that incorporation of chromophores in the side chains of polymers towards the polystyrene moiety increases the rigidity of the polymer and subsequently, its glass transition temperature; however the incorporation of side chain towards the alcoholic functional group decreases the glass transition temperature. The post derivatives do not play any significant role to increase the thermal stability (TGA). There was evidence for liquid crystalline properties in the resulting polymer derivative DXPSt (P4) as observed from POM study, which defines the alignment of chromophores into the polymers. The XRD study shows crystalline behaviour of the polymer derivative, P4. The polymer derivative, DXPSt (P5) does not show such behaviour and this may be due to the bonding of azomethine towards the short chain alcoholic telechelic alcoholic sides of the copolymer.

Second-order Phase Transition Behavior in a Polymer above the Glass Transition Temperature

2021 ◽  
Author(s):  
Mitsuru Ishikawa ◽  
Taihei Takahashi ◽  
Yu-ichiro Hayashi ◽  
Maya Akashi ◽  
Takayuki Uwada
Keyword(s):  
Phase Transition ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Order Phase Transition ◽  
Second Order ◽  
Critical Slowing Down ◽  
Phase Transition Behavior ◽  
Slowing Down ◽  
Second Order Phase Transition

<p>Glass transition was primarily considered to be not phase transition; however, it has similarity to the second-order phase transition. Recent single-molecule spectroscopy developments have prompted re-investigating glass transition at the microscopic scale, revealing that glass transition includes phenomena similar to second-order phase transition. They are characterized by microscopic collective polymer motion and discontinuous changes in temperature dependent relaxation times, later of which is similar to critical slowing down, within a temperature window that includes the polymer calorimetric glass transition temperature. Considering that collective motion and critical slowing down are accompaniments to critical phenomena, second-order phase transition behavior was identified in polymer glass transition.</p>

Curing, Thermal and Mechanical Properties of Liquid Crystalline p-SBPEPB/BPAER/DDE System

2011 ◽  
Vol 239-242 ◽  
pp. 3253-3256 ◽  
Author(s):  
Li Huo ◽  
Jun Gang Gao ◽  
Yong Gang Du
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Impact Strength ◽  
Bisphenol A ◽  
Liquid Crystalline ◽  
Curing Agent ◽  
Thermal And Mechanical Properties ◽  
Component System

The curing, thermal and mechanical properties of bi-component system for bisphenol A epoxy resin (BPAER) modified by liquid crystalline Sulfonyl bis(4,1-phenylene)bis[4-(2,3-epoxypro pyloxy)benzoate] (p-SBPEPB), with 4,4'-diaminodiphenyl ether (DDE) as a curing agent, were investigated. The effect of the different liquid crystalline contents and the heating rate on curing reaction was discussed. The results show that the curing peak temperature decreases, curing rate increases, the glass transition temperature (Tg)and impact strength all increase with adding of liquid crystalline p-SBPEPB when the content is not over 8wt%.

scholarly journals Second-order Phase Transition Behavior in a Polymer above the Glass Transition Temperature

2020 ◽  
Author(s):  
Mitsuru Ishikawa ◽  
Taihei Takahashi ◽  
Yu-ichiro Hayashi ◽  
Maya Akashi ◽  
Takayuki Uwada
Keyword(s):  
Phase Transition ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Single Molecule ◽  
Order Phase Transition ◽  
Collective Motion ◽  
Relaxation Times ◽  
Second Order ◽  
Second Order Phase Transition

Glass transition was primarily considered to be not phase transition; instead, regarded as pseudo secondorder phase transition due to its similarity to the ordinary second-order phase transition. Recent single-molecule spectroscopy developments have prompted re-investigating glass transition at the microscopic scale, confirming that the initial classification is correct and revealing that glass transition includes phenomena similar to second-order phase transition. They are characterized by microscopic collective polymer motion and discontinuous changes in temperature dependent relaxation times within a temperature window that includes the polymer calorimetric glass transition temperature. Generally, atom or molecule collective motion and discontinuous changes in physical quantities including relaxation times characterize critical phenomena associated with second-order phase transitions near specific temperatures. Thus, second-order phase transition phenomena are involved in polymer glass transition.

Investigation of thermochromism in a series of side-chain, liquid-crystalline, azobenzene-containing polymers

2004 ◽  
Vol 82 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Stephan Freiberg ◽  
François Lagugné-Labarthet ◽  
Paul Rochon ◽  
Almeria Natansohn
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Liquid Crystalline ◽  
Electronic Absorption Spectra ◽  
Side Chain ◽  
Hypsochromic Shift ◽  
Vis Spectroscopy ◽  
Thermochromic Properties

The thermochromic properties of a series of liquid crystalline polymethacrylates, containing azobenzene side-chains with variable spacer lengths, were investigated. Annealing the amorphous polymer thin films above the glass transition temperature results in a rearrangement of the azobenzene moieties, causing a hypsochromic shift in the electronic absorption spectra. A detailed investigation of the spectral shift was performed by in situ UV–vis spectroscopy and indicated the formation of H-type aggregates by the side-chain chromophores above the glass transition temperature. The rate at which the hypsochromic shift occurs is faster for polymers with shorter spacers since their high glass transition temperature results in a higher thermal energy during the thermochromic effect. Experimentally determined activation energies show that the aggregation occurs primarily due to side-chain relaxation (β-relaxation) and main-chain relaxation (α-relaxation). Further annealing above the isotropization temperature resulted in the onset of deaggregation and in most cases showed that the chromophores were freed from the ordered state.Key words: liquid-crystalline polymer, thermochromic properties, chain relaxation, aggregation, thin films, azobenzene mesogens.

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