Viscoelasticity based block copolymers

G. Kraus, K.W. Rollmann, and R.A. Gray, "Tack and Viscoelasticity of Block Copolymer Based Adhesives," J. Adhesion, 221 (1979). 

Ren, J., SUva, A. S., and Krishnamoorti, R., Linear viscoelasticity of disordered polystyrene-polyisoprene block copolymer based layered-silicate nanocomposites. Macromolecules, 33, 3739-3746 (2000). 

There have been very few studies reported on the viscoelastic properties of rubber-resin pressure sensitive adhesive systems. In 1973, M. Sherriff and co-workers (1) reported on the effect of adding poly (j3-pinene) resin to natural rubber. Based on a G master curve, they showed that the resin shifted the entry to the transition zone to a lower frequency and reduced the modulus in the rubbery plateau. G. Kraus and K.W. Rollman (2) reported in 1977 on their study of resins blended with styrene-isoprene-styrene block copolymers. They showed that the addition of a resin increased the glass transition temperature of the rubbery mid-block and decreased the plateau modulus. Accordingly, a satisfactory tackifying resin should produce these changes. 

The viscoelastic effects on the morphology and dynamics of microphase separation of diblock copolymers was simulated by Huo et al. [ 126] based on Tanaka s viscoelastic model [127] in the presence and absence of additional thermal noise. Their results indicate that for

bulk modulus of both blocks, the area fraction of the A-rich phase remains constant during the microphase separation process. For each block randomly oriented lamellae are preferred. 

Rheological measurements also show that PS-PI diblock and PS-P1-PS triblock copolymers with /< 0.2 (for either block) exhibit a liquid-like viscoelastic response, even at temperatures below the ODT (Adams et al. 1994 Han et al. 1995 Sakamoto et al. 1997). Han et al. (1995) and Sakamoto et al. (1997) have observed that the ODT cannot be located for these samples based on a discontinuity in the isochronal shear moduli as a function of temperature but can be obtained from plots of logG versus logG" (Fig. 2.4(c)). 

Lee and Han (2003b) investigated linear dynamic viscoelastic properties of organoclay nanocomposites based on both SI diblock copolymer and SIOH diblock copolymer. An SIOH diblock copolymer (referred to as SI-14/3-OH) was obtained by hydroxylation of the polyisoprene (PI) block of a highly asymmetric SI diblock copolymer (SI-14/3, with Af = 1.7 x 10" and = 1.08). SI-14/3 was a... 

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