Polybutadienes solution properties

The solution properties of dendrigraft polybutadienes are, as in the previous cases discussed, consistent with a hard sphere morphology. The intrinsic viscosity of arborescent-poly(butadienes) levels off for the G1 and G2 polymers. Additionally, the ratio of the radius of gyration in solution (Rg) to the hydrodynamic radius (Rb) of the molecules decreases from RJRb = 1.4 to 0.8 from G1 to G2. For linear polymer chains with a coiled conformation in solution, a ratio RJRb = 1.48-1.50 is expected. For rigid spheres, in comparison, a limiting value RJRb = 0.775 is predicted. 

Relaxation curves recorded from polybutadiene solutions have been shown to satisfy such a property, provided measurements are performed at a temperature higher than a temperature threshold which will be called Tg, hereafter Tg is higher than the Tg glass transition temperatiure of the polymeric system (Tg - Tg = 80K). Above tms temperature threshold, the mathematical structure of the relaxation fimction is kept invariant except for the time scale. Because of the property of superposition, normalized relaxation curves can be characterized by chosing a given amplitude A and by measuring the time interval corresponding to this amplitude... 

UTR Utracki, L.W., Simha, R., and Fetters, L.J., Solution properties of polystyrene-polybutadiene block copolymers, J. Polym. Sci. PartA-2,6, 2051,1968. 

Utracki, L. A., Simha, R Fetters L. J Solution properties of polystyrene-polybutadiene block copolymers. Journal of Polymer Science Part A-2, Polymer Physics, 6(12), pp. 2051-2066 (1968). 

Budene solution polybutadiene (solution polymerized) is cis-1,4-poly(butadiene) produced with stereospecific catalysts which yield a controlled MWD, which is essentially a linear polymer. Butadiene rubber, polybutadiene, is solution-polymerized to stereospecific polymer configurations " by the additional polymerization of butadiene monomer. The following cis- and trans-1,4-polybutadiene isomers can be produced cis-1,4-polybutadiene with good dynamic properties, low... 

Among branched polymers, star polymers represent the most elementary way of arranging the subchains since each star contains only one branching point, and as such, they serve as useful models for experimental evaluation of theories about solution properties and rheological behavior of branched polymers (Angot et al., 1998). Star polymers nd applications as additives in various areas such as rheology modi ers, pressure sensitive additives, etc. Besides serving as additives, star polymers can also be used as such to achieve sped c properties. For instance, star block copolymers with polystyrene-fc-polybutadiene (PSt-fo-PB) arms have better processability and me-... 

Among the techniques employed to estimate the average molecular weight distribution of polymers are end-group analysis, dilute solution viscosity, reduction in vapor pressure, ebuUiometry, cryoscopy, vapor pressure osmometry, fractionation, hplc, phase distribution chromatography, field flow fractionation, and gel-permeation chromatography (gpc). For routine analysis of SBR polymers, gpc is widely accepted. Table 1 lists a number of physical properties of SBR (random) compared to natural mbber, solution polybutadiene, and SB block copolymer. 

Chain Length Properties of the Modified Polymers. A number of partially hydrogenated and hydroxymethyl ated polybutadienes were analyzed using vapour pressure osmometry, dilute solution viscometry and gel permeation chromatography. The parent polybutadiene had Mn in the range of 9,000 to 50,000. In the case of vapour pressure osmometry, the data were reproducible for polymers with Mn less than 20,000. All the polymers obtained (hydrogenated and... 

The information on physical properties of radiation cross-linking of polybutadiene rubber and butadiene copolymers was obtained in a fashion similar to that for NR, namely, by stress-strain measurements. From Table 5.6, it is evident that the dose required for a full cure of these elastomers is lower than that for natural rubber. The addition of prorads allows further reduction of the cure dose with the actual value depending on the microstructure and macrostructure of the polymer and also on the type and concentration of the compounding ingredients, such as oils, processing aids, and antioxidants in the compound. For example, solution-polymerized polybutadiene rubber usually requires lower doses than emulsion-polymerized rubber because it contains smaller amount of impurities than the latter. Since the yield of scission G(S) is relatively small, particularly when oxygen is excluded, tensile... 

In solution, block copolymers display interesting colloidal and interfacial properties. They can be used as emulsifying agents in water-oil and oil-oil systems (6 ). In the later case, the oil phases are solid and they give rise to polymeric alloys (7.) or they are liquid and they allow the preparation of latexes in organic medium (8 ). However, the molecular structure of block copolymers based on polybutadiene PB (70 ) and polystyrene PS behave as thermoplastic elastomers when engaged in multiblock (PB-PS)n or triblock (PS-PB-PS) structures but never when implied in inverse triblock or diblock arrangements. Similarly the... 

The viscoelastic properties of solutions of linear and 4-armed star polybutadienes were studied by Osaki and co-workers (117), who compared the storage and loss shear moduli extrapolated to zero concentration with theoretical values. The results for the branched polymer could be accounted for well in terms of the Zimm and Kilb theory (34) a lower value of the hydrodynamic interaction parameter was indicated for the branched polymer than for the linear one, which may be associated with the higher density of polymer segments in the former. 

The specific volume and expansion coefficient of the solution-blended material are shown in Figure 6, along with data for pure polybutadiene and pure polystyrene. None of the three polymers has any distinguishing features below the polystyrene Tg> illustrating that the observed transition and minimum are the results of the unique structural morphology of the block copolymers. It should be noted that the substantial difference in the thermal expansion coefficients of polybutadiene and polystyrene can be expected to be an important factor affecting the structure and properties of block copolymer samples prepared under various conditions. 

The system utilized in Figure 3.13 for HIPS can also be used to produce a solution polymerization ABS. This type of ABS is used in non-glossy applications. The glossy ABS is usually produced in an emulsion process in which emulsified polybutadiene latex is grafted and agglomerated and blended with a continuous phase of SAN. This blended material is then dried and pelletized. This process is not cost competitive with the continuous solution polymerization, but it produces a product with a superior balance of properties that commands a premium price. 

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