Glass Transition Behavior of Polyisoprene: The Influence of Molecular Weight, Terminal Hydroxy Groups, Microstructure, and Chain Branching

1982 ◽  
Vol 55 (1) ◽  
pp. 245-252 ◽  
Author(s):  
C. Kow ◽  
M. Morton ◽  
L. J. Fetters ◽  
N. Hadjichristidis
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Low Molecular Weight ◽  
Hydroxyl Groups ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Chain Branching ◽  
Glass Transition Temperatures ◽  
Hydroxy Groups

Abstract The glass transition temperatures for a series of high-1,4 linear and star-branched polyisoprenes have been measured by differential scanning calorimetry. The Fox-Flory relation for the linear polyisoprenes was found to be Tg=Tg∞−1.76×104Mn−1. The influence of hydroxyl groups on Tg was also examined for low molecular weight (<2.2×104) polyisoprenes.

scholarly journals Copolymerization of Norbornene and Styrene with Anilinonaphthoquinone-Ligated Nickel Complexes

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1100 ◽  
Author(s):  
Chowdhury ◽  
Tanaka ◽  
Nakayama ◽  
Shiono
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Catalytic System ◽  
Nickel Complexes ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Glass Transition Temperatures ◽  
Structural Characterizations

Poly(norbornene-co-styrene)s were synthesized by the use of anilinonaphthoquinone-ligated nickel complexes [Ni(C10H5O2NAr)(Ph)(PPh3): 1a, Ar = C6H3-2,6-iPr; 1b, Ar = C6H2-2,4,6-Me; 1c, Ar = C6H5] activated with modified methylaluminoxane (MMAO) or B(C6F5)3 in toluene. The effects of the cocatalysts were more significant than those of the nickel complexes, and MMAO gave higher activity than B(C6F5)3. The structural characterizations of the products indicated the formation of statistical norbornene copolymers. An increase of the styrene ratio in feed led to an increase in the incorporated styrene (S) content of the resulting copolymer. The molecular weight of the copolymer decreased with increasing the S ratio in feed at 70 °C. The copolymerization activity, using MMAO as a cocatalyst, decreased with lowering of the temperature from 70 to 0 °C, accompanied by an increase in the molecular weight of the copolymer. The S incorporation up to 59% with Mn of 78,000 was achieved by the 1b-B(C6F5)3 catalytic system. The glass transition temperatures of the norbornene (N)/S copolymers determined by differential scanning calorimetry, decreased from 329 to 128 °C according to the S content.

Synthesis and Properties of Poly (N-arylenebenzimidazole ketone)s

2014 ◽  
Vol 881-883 ◽  
pp. 165-168
Author(s):  
Xiang Wang Cui ◽  
Lin Zhang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Coupling Reaction ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Glass Transition Temperatures

Two bis (benzimidazoyl) monomers were synthesized, and Poly (N-arylenebenzimidazole ketone) s were prepared by N-C coupling reaction that replaced the NH sites from the bis (benzimidazolyl) derivatives with activated difluorides monomers in sulfolane at 210 °C. All the resulting polymers showed easy solubility compared with traditional polybenzimidazoles. Differential scanning calorimetry and thermogravimetric measurements showed that the polymers had high glass transition temperatures (>240 °C), good thermostability and high decomposition temperatures (>460 °C).

Effect of Molecular Weight on Glass Transition by Differential Scanning Calorimetry

1974 ◽  
Vol 52 (18) ◽  
pp. 3170-3175 ◽  
Author(s):  
Louis-Philippe Blanchard ◽  
Jean Hesse ◽  
Shadi Lal Malhotra
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Glass Transition ◽  
Heating Rate ◽  
Low Molecular Weight ◽  
Glass Transitions ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Polystyrene Sample

The influence of molecular weight (900 to 1.8 × 106) on the glass transition temperature of low polydispersity polystyrene (anionically prepared) has been studied by differential scanning calorimetry at heating rates of 5 to 80 °C min−1. Over the range of molecular_weight studied, and at an extrapolated heating rate of 1 °C min−1,[Formula: see text] A thermally prepared polystyrene sample ([Formula: see text]and Pd = 3.2) showed a Tge value of 93 °C, some 10° below the value predicted by the above equation. Low molecular weight species in the highly polydisperse sample are believed to be responsible for the discrepancy. The changes in heat capacity brought about by the glass transitions are accompanied in all cases on heating by an endothermic peak and this regardless of the heating rate (even extrapolated to 1 °C min−1) or the molecular weight of the sample, suggesting that the glass transition phenomenon encountered with polystyrene is a process involving a positive heat effect.

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