Properties of low molecular weight block copolymers. 1. Differential scanning calorimetry of styrene-dimethylsiloxane diblock copolymers

1982 ◽  
Vol 15 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Sonja Krause ◽  
Magdy Iskandar ◽  
Mohammad Iqbal
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Block Copolymers ◽  
Diblock Copolymers ◽  
Low Molecular Weight ◽  
Scanning Calorimetry

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.

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.

Block Copolymers Poly(2,6-dimethyl-1,4-phenylene oxide)-poly(6-hexanelactam). Preparation and Composition

1993 ◽  
Vol 58 (11) ◽  
pp. 2574-2582 ◽  
Author(s):  
Jaroslav Stehlíček ◽  
Rudolf Puffr
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Diblock Copolymer ◽  
Anionic Polymerization ◽  
Diblock Copolymers ◽  
Toluene Solution ◽  
Low Molecular Weight ◽  
Phenylene Oxide ◽  
End Groups ◽  
Tolylene Diisocyanate

Poly(2,6-dimethyl-1,4-phenylene oxide)-poly(6-hexanelactam) diblock copolymers were prepared from low-molecular weight poly(2,6-dimethyl-1,4-phenylene oxide) by transforming its phenolic end groups via the reaction with 2,4-tolylene diisocyanate and 6-hexanelactam to polymeric initiators and the subsequent anionic polymerization of 6-hexanelactam. The polymerization of 6-hexanelactam was carried out in bulk or toluene solution. The content of the 6-hexanelactam homopolymer was estimated by TLC showing that the pure diblock copolymer can be prepared in toluene. The reason for relatively low yields is discussed.

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