Diblock copolymers definition

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

A simple mean field theory for micelle formation by a diblock copolymer in a homopolymeric solvent was developed by Leibler et al. (1983). This model enables the calculation of the size and number of chains in a micelle and its free energy of formation. The fraction of copolymer chains aggregating into micelles can also be obtained. A cmc was found for low copolymer contents even for weak incompatibilities between components. Leibler et al. (1983) emphasize that fora finite aggregation number p, the cmc is a region rather than a well-defined concentration and some arbitrariness is involved in its definition. 

Taking all the fact presented in this section into account, together with the synthesis method and fractionation results, we conclude that the purified copolymer separated from reaction products is an iPS-fo-iPP diblock copolymer consisting of iPS and iPP blocks it is definitely not a simple blend of homopolymers. On the other hand, the distinctive characteristics of the copolymers crystallization kinetics also indicate that, compared with homopolymers and the iPS-iPP blend, the purified copolymer is a true iPS-fo-iPP diblock copolymer (23). 

Definition Produced by coupling S/B diblock copolymers into a S-B-S triblock with typical 30% styrene content... 

Classification Thermoplastic elastomer Definition Produced by coupling styrene-isoprene diblock copolymers into S-l-S triblock with typical styrene content of 14%... 

A—B diblock copolymers adsorb spontaneously at the interface between two immiscible A and B homopolymers. Our objective here is to make quantitative predictions of the nature of the adsorbed layer, fri this case, the phase behavior depends on (Mily one x parameter, that between the A and B homopolymers, and the statistical segment lengths of the A and B chains. The specific example that we will smdy is the adsorption of a SPB(89)-SPB(63) diblock copolymer at the interface between SPB(89) and SPB(63) homopolymers at room temperamre [A = SPB(89) and B = SPB(63)]. For this system, x = 0.0064 (system 33 in Table 19.1), I A = 0.49 nm, and /b = 0.75 nm. We consider the interface between SPB(89) and SPB(63) homopolymers with Na = 4,230 and Nr =3,600. It is straightforward to show that the two homopolymeis are highly immiscible because xAave =6.2 which is much greater than 2 (see Eq. (19.8) for definition of Nave)- We consider the adsorption of a SPB(89)-SPB(63) diblock copolymer with NAb = 790 and Nsb = 730 where the subscript b refers to the chains comprising the block copolymer. We consider two flat homopolymer-rich phases with the diblock copolymer adsorbed at the interface. The z-axis of our coordinate frame is perpendicular to the interface. The results of SCFT predictions for 0 e volume fraction of the A-B... 

Significantly, DEER measurements also provided intercluster distances for the homopolymers, for which the ionic peak cannot be detected reliably in SAXS curves, and for the diblock copolymers, where it cannot be detected at all. The scaling coefficient x in r = AMn for the intercluster distances r with molecular weight Mn provides information on the spatial distribution of the clusters. In earlier work on a, tw-dicarboxylatopolybutadienes and a, molecular weights was too narrow for a definite conclusion about... 

This is called the saddle point approximation, and the resulting theory is equivalent to the mean-field theory. In practice, the coarse grained states are defined in terms of an order parameter that by definition has a value 0 in the disordered phase and a nonzero value in the ordered state. In the case of AB diblock copolymers, this order parameter is defined as the deviation of the A monomer fraction from the average value. Since this order parameter is a function of position, it actually represents infinitely many variables. By definition, in the weak segregation regime, the order parameter is small and it is meaningful to expand Fi in a Taylor series. 

There can be two definitions of the term compatibilization . The first is the process of reinforcement of the interfacial border in an immiscible polymer blend. The physical essence consists of increasing the interaction between two phases by introduction of substances like diblock polymers, when dissimilar blocks of copolymer will locate at the phase interface. Such com-patibilizers do not change the thermodynamic stability of the system and at the same time vary the morphology of the composition, leading to a more fine dispersion of components in the course of blending. 

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