Rheological behaviour of block copolymers in the disordered state: effects of molecular weight and block length ratio

Polymer ◽  
1992 ◽  
Vol 33 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Chang Dae Han ◽  
Deog Man Baek ◽  
Jin Kon Kim ◽  
Sung Gun Chu
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Rheological Behaviour ◽  
Length Ratio ◽  
Block Length

Structure-Property Relationships of Perfectly Alternating Polycarbonate-Polydimethylsiloxane Block Copolymers, Part II

1984 ◽  
Vol 57 (1) ◽  
pp. 184-202 ◽  
Author(s):  
S. H. Tang ◽  
E. A. Meinecke ◽  
J. S. Riffle ◽  
J. E. McGrath
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Block Copolymers ◽  
Dynamic Mechanical Properties ◽  
Block Length ◽  
Structure Property ◽  
Two Phase ◽  
K Value ◽  
Mechanical Coupling ◽  
Molecular Weights

Abstract The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.

Elastomeric Polycarbonate Block Copolymers

1965 ◽  
Vol 38 (2) ◽  
pp. 431-449
Author(s):  
Eugene P. Goldberg
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Bisphenol A ◽  
Flexural Modulus ◽  
Softening Temperature ◽  
Thermoplastic Elastomers ◽  
Partial Replacement ◽  
Initial Increase ◽  
Copolymer Composition ◽  
Moderate Degree

Abstract Polycarbonate block copolymers were prepared by phosgenating pyridine solutions of polyether glycol-bisphenol-A mixtures. Copolycarbonates derived from poly(oxyethylene) glycols (Carbowaxes) were studied in detail for property-structure effects as a function of glycol molecular weight (1000–20,000) and copolymer composition (5–70 weight per cent or 0.3–10.0 mole per cent of a 4000 molecular weight glycol). Remarkable strength (>7000 psi) and snappy elasticity (>90 per cent immediate recovery) were observed at poly(oxyethylene) block concentrations greater than 3 mole per cent. These thermoplastic elastomers also exhibited high softening temperatures (>180° C) and tensile elongations up to about 700 per cent. Both Tg and softening temperature varied linearly with comonomer mole ratio over the composition range studied, with Tg displaying much greater polyether concentration sensitivity. It is suggested that the observed property effects result to a large extent from the variation in poly(bisphenol-A carbonate) block length that accompanies the changing of copolymer composition. An initial increase in flexural modulus (stiffness) was observed at low polyether concentrations (0–1 mole per cent). This phenomenon is considered to be related to similar modulus effects found in plasticized rigid thermoplastics at low plasticizer concentrations. A moderate degree of molecular order, due to bisphenol carbonate segments rather than the normally crystalline polyether, was detected by x-ray analysis. Elastomeric carbonate-carboxylate tetrapolymers were also prepared by partial replacement of carbonate with isophthalate, terephthalate or adipate linkages in polyether-bisphenol systems. The dramatic softening temperature depression observed in this class of polymers is attributed to the disruption of long bisphenol carbonate block sequences that exist in the simpler polyether glycol-bisphenol carbonate copolymers.

Effect of Block Molecular Weight on the Mechanical Properties of PA1010-b-PEG Segmented Block Copolymers

2012 ◽  
Vol 512-515 ◽  
pp. 2127-2130
Author(s):  
Li Huo ◽  
Cai Xia Dong
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Block Copolymers ◽  
Microphase Separation ◽  
Soft Segment ◽  
Mechanical Measurements ◽  
Wide Range ◽  
Hard Block ◽  
Higher Temperature ◽  
Hard Segments

The mechanical properties were investigated of a series of PA-PEG thermalplastic elastomer based on PA1010 and polytetramethylene glycol (PEG) with varying hard and soft segment content. Dynamic mechanical measurements of these polymers have carried out over a wide range of temperatures. The block copolymers exhibit three peaks, designated as α, β and γ in the tanδ-temperature curve. The α transition shifts to higher temperature with increasing hard block molecular weight. However, at a constant hard molecular weight, the α transition shifts to higher temperature and the damping increases on increasing the soft segment molecular weight. DMA results show that the block copolymers exhibit a microphase separation structure and both soft and hard segments were found to be crystallizable. The degree of phase separation increases with increasing hard block molecular weight.

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