Block polymers notation

The samples used in this study are listed in Table I with selected characterization data. Also given are our notations for the samples. S and B represent polystyrene and polybutadiene, respectively. The block polymers are denoted S/Bi, S/B2, etc. The letters identify the polymer components with the first letter indicating the center segment. The polymers were isolated from the polymerization solution by precipitation into cold (0°C), well-stirred methanol. After careful drying in a vacuum oven (25°C), film samples were prepared by melt pressing at temperatures ranging from 25 °C for homopolybutadiene to 150 °C for homopolystyrene. 

There are many notations for representing block polymers. We have followed the most common in using A to represent a block of A mer units, with similar representation for B, C, etc., as shown in Table I. Here A-B represents a two block polymer, A-B-C a three block polymer, and A-B-A represents a three block polymer with A terminal blocks and B center blocks. (A-B)jj represents a linear multiblock polymer of alternating A and B blocks. 

In this notation A and B can represent different stereo configurations, or microstructures of the same mer. Likewise, either A and/or B may be random or tapered copolymer blocks rather than homopolymeric blocks. A tapered A-B block is one that begins with a section of pure A mers and gradually incorporates B mers until at the end it becomes a section of pure B mers. The A-B-C designation represents the incorporation of a third monomer segment and would most probably comprise a three-phase system. An A-B-A block polymer based on styrene and butadiene would mean in this notation a polystyrene block-polybutadiene block-polystyrene block structure, that is, S-B-S. 

In order to introduce some notation and definitions, we consider a polymer block with n monomers of segment length b. Defining Ti as the interdistance between two monomers i and j in that block, and Q as the scattering wave-number (often called scattering vector ), various types of correlations can be considered depending on the number of summations involved ... 

Related to the run number R is the number average sequence length (N.A.S.L.), which is defined for a monomer A in an AB copolymer as the total number of A monomers in the polymer chain divided by the total number of blocks of monomer A (regardless the block length) [5]. Using the notation n(A) for N.A.S.L., the expression for n(A) is the following ... 

A standard notation for block copolymers is becoming accepted, whereby X-b-Y denotes a diblock copolymer of polymer X and polymer Y. However, sometimes the b is replaced by the full term block, or alternatively is omitted, and the diblock denoted X-Y. 

Figure 3 Reflectivity profile R as a function of Ao the neutron momentum perpendicular to the film surface (Ab=p, in our notation in Rgures 1 and 2). ° The inset shows the deduced layer profile in units of the scattering length density as a function of the distance z with z= 0 at the free surface. The multilayer stmcture is very clearly obtained due to the deuteration of the PS block, which enhances the SLD contrast between the two polymer blocks in the P(d-S-b-MMA) compound. The theoretical background of how to treat multilayers in the data analysis is discussed in Box 2.

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