Conformation of isolated block copolymer molecules

Zero-Shear Viscosity of Block Copolymers in Semidilute Solutions

“…The dependences of 11~ on C [11] in pyridine (a commonly good solvent) and MEK (a commonly poor solvent) agree with those predicted by eq 3 with v = 0.58 and 0.53, respectively, whereas the dependence of 17~ on C [11] in benzene (a selective solvent) is lower than that predicted by eq 3 with v = 0.55.…”

“…3 In semidilute solutions where C « 1, but C/C*» I, 11~ is given by a scaling law as 4 -6 11~0 (( C/C*Y4,4-3v)/(3v-1) CX:( C[ 11 JY4.4-3v)/(3v-1) (3) where v is the exponent in the relationship between radius of gyration and molecular weight, <s 2 ) ex: M 2 v. Here, the second equation is also derived assuming the Flory-Fox equation. Thus, 11~ is predicted to be expressed as a universal function of (C/C*) or C [11] in both the dilute and semidilute regions, and this theoretical prediction was confirmed by experiments as reported previously. 5 ' 6 In block copolymer solutions, microphase separation occurs above a critical concentration even in commonly good solvents.…”

“…In Figures 4--6, the data in for 11° of homopolymers in entangled regions also holds for the block copolymer solutions where the concentration is high enough. Figures 7-9 show the viscosity data replotted in the double logarithmic form of 11~ vs. C [11]. These figures · show that 11~ of a block copolymer is expressed as a universal function of C [17] in both dilute and semidilute solutions in the same way as that of homopolymer.…”

“…In dilute solutions where C« I and C/C*« 1, the reduced zero-shear viscosity 11~ is given by 11~ = 11?p/C [11] = 1 + k' C [11] + · · · = I + kC/ C* + · · · (2) where 11?P = (11° -11s)/11., 11s is the solvent viscosity, [ 11] is the intrinsic viscosity, k' is the Huggins' constant, and k=3k''1>'/(4nNA)-Here, the last equation is obtained by assuming the Flory-Fox equation, [11] = cJ>'<s 2 ) 312 /M where cJ>' is the Flory viscosity factor. 3 In semidilute solutions where C « 1, but C/C*» I, 11~ is given by a scaling law as 4 -6 11~0 (( C/C*Y4,4-3v)/(3v-1) CX:( C[ 11 JY4.4-3v)/(3v-1) (3) where v is the exponent in the relationship between radius of gyration and molecular weight, <s 2 ) ex: M 2 v. Here, the second equation is also derived assuming the Flory-Fox equation.…”

“…It was found that the reduced zero-shear viscosity I'/~ ( = 1'/~p/C[11]) is expressed as a universal function of C [11] in all solvents, and the dependence of I'/~ on C[11] is determined by the exponent in the relationship between the radius of gyration and molecular weight of the block component which has the larger excluded volume, regardless of the solvent.KEY WORDS Zero-Shear Viscosity / Block Copolymer / Scaling Theory / Solvent Effect / …”