Blockiness

Particle shapes are classified as acicular. A, monoclinic and blocky, M, or monoclinic and needle, N. 

Aluminosilicates. These silicates consist of frameworks of silica and alumina tetrahedra linked at all corners to form three-dimensional networks familiar examples are the common rock-forming minerals quartz and feldspar. Framework silicates generally form blocky crystals, more isotropic... 

Fig. 3. Influence of vinyl alcohol—vinyl acetate copolymer composition on melting temperature (56), where A represents block copolymers B, blocky...

The living polymerization process offers enormous flexibiUty in the design of polymers (40). It is possible to control terminal functional groups, pendant groups, monomer sequencing along the main chain (including the order of addition and blockiness), steric stmcture, and spatial shape. 

When both and T2 are greater than 1, the copolymer becomes blocky ia nature. When and T2 are much greater than 1, homopolymers of each monomer are formed and the resulting material is usually a polymer blend of some copolymer and homopolymer. Type II ... 

These values assume chlorination in carbon tetrachloride solution under homogeneous conditions favoring random distribution of chlorine atoms along the chain. Viscous reaction conditions, faster chlorine addition rates, lower temperature conditions, etc, can lead to higher AH at equivalent chlorine levels because of more blocky chlorine distribution on the polymer chain. 

Using proton NMR of solutions, the composition of polymers can be analyzed.47 Carbon-13 NMR spectroscopy is a useful tool for studying the sequence length of segments in copolymers and thereby determining the blockiness of the copolymer. With solid-state NMR, the mobility of chain segments can be studied and the crystallinity determined. 

Produces strong, blocky coke having good reactivity. Involves low capital and running costs. Production process delinks with availability of markets for byproducts. Allows shut down without any detrimental effects to refractory. Produces hard coke for foundry. The process is characterized by simplicity. There involves no requirements of extra fuel for heating as in by-product oven practice. 

To produce elastomeric materials from 95, Kolel-Veetil and Keller studied the effects of reducing the concentration of the diacetylene units in 95 on the plasticities of the resulting networks.127 The ratio (1 2 1) of the carborane, disiloxane, and diacetylene moieties in 95 was altered to 2 3 1, 4 5 1, and 9 10 1, respectively, to produce polymers containing progressively lower amounts of diacetylene units. Two sets of the polymers, one an alternating type (97) and the other a blocky type (98) (Fig. 60), were synthesized. The networked polymers produced from both the blocky and the alternating sets were found to be slightly elastomeric with T values around... 

Figure 60 The synthetic schemes for the diacetylene-diluted (a) alternating (97) (left) and (b) blocky poly( -carborane-disiloxane-diacetylene)s (98). (Adapted from ref. 127.)...

Abstract Protein-like copolymers were first predicted by computer-aided biomimetic design. These copolymers consist of comonomer units of differing hydrophilicity/hydro-phobicity. Heterogeneous blockiness, inherent in such copolymers, promotes chain folding with the formation of specific spatial packing a dense core consisting of hydrophobic units and a polar shell formed by hydrophilic units. This review discusses the approaches, those that have already been described and potential approaches to the chemical synthesis of protein-like copolymers. These approaches are based on the use of macromolecular precursors as well as the appropriate monomers. In addition, some specific physicochemical properties of protein like copolymers, especially their solution behaviour in aqueous media, are considered. 

Keywords Chemical synthesis Heterogeneous blockiness Physicochemical studies Protein-like copolymers Solution behaviour... 

The third approach (iii), the solid-phase synthesis, has not been yet implemented for the preparation of protein-like HP-copolymers with heterogeneous blockiness, although the possibility—inherent in this method—to form the macromolecular chains with a well-defined chemical sequence of monomeric units is of great interest for the problem. That is why, these possibilities will also be discussed briefly in Sect. 2.4. 

By varying all the parameters of the process the authors prepared a set of copolyesters containing units and blocks with a tertiary amino group, which, in turn, could be transformed into a hydrophilic hydrochloride salt thus imparting water-compatibility to the initially organosoluble macromolecules. The principle involved was the formation of a block-type structure of chains in order to facilitate their further protein-like folding in an aqueous medium. It was shown that the main factors responsible for the blockiness were the relative reactivities of the (B) and (C) components (NMDEA and bisphenol) and the order of their addition to the reaction. 

Table 3 demonstrates the influence of the latter factor on the microheterogeneity coefficient (Km) for the case of polycondensation of terephthaloyl dichloride (A) with NMDEA (B) and phenolfluorene (C). This coefficient is computed from the data of H NMR spectra of corresponding copolyesters. It characterizes the relative content of different triades in a copolymer the smaller the Km value, the higher the blockiness of the chains [61]. 

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