Polystyrene molecular structure

Fig. 2. Molecular structures of selected photoconductive polymers with pendent groups (1) poly(A/-vinylcarba2ole) [25067-59-8] (PVK), (2) A/-polysiloxane carbazole, (3) bisphenol A polycarbonate [24936-68-3] (4) polystyrene [9003-53-6] (5) polyvin5i(l,2-/n7 j -bis(9H-carba2ol-9-yl)cyclobutane) [80218-52-6]...

There are at the present time many thousands of grades of commercial plastics materials offered for sale throughout the world. Only rarely are the properties of any two of these grades identical, for although the number of chemically distinct species (e.g. polyethylenes, polystyrenes) is limited, there are many variations within each group. Such variations can arise through differences in molecular structure, differences in physical form, the presence of impurities and also in the nature and amount of additives which may have been incorporated into the base polymer. One of the aims of this book is to show how the many different materials arise, to discuss their properties and to show how these properties can to a large extent be explained by consideration of the composition of a plastics material and in particular the molecular structure of the base polymer employed. 

Amorphous thermoplastics These are made from polymers which have a sufficiently irregular molecular structure to prevent them from crystallising in any way. Examples of such materials are polystyrene, poly methyl methacrylate and polyvinyl chloride. 

When this procedure is applied to the data shown for polystyrene in Fig. 116 and to those for polyisobutylene shown previously in Fig. 38 of Chapter VII, the values obtained for t/ i(1 — /T) decrease as the molecular weight increases. The data for the latter system, for example, yield values for this quantity changing from 0.087 at AT-38,000 to 0.064 at ilf = 720,000. This is contrary to the initial definition of the thermodynamic parameters, according to which they should characterize the inherent segment-solvent interaction independent of the molecular structure as a whole. 

Fig. 9 (a) Molecular structures of novel ESIPT dyes, 2,5,-bis[5-(4-t-butylphenyl)-[l,3,4]oxadia-zol-2-yl]-phenol (SOX), and 2,5-bis[5-(4-t-butylphenyl)-[l,3,4]oxadiazol-2-yl]-benzene-l,4,-diol (DOX). (b) Emission colors in the Commission Internationale de L Eclariage (CEE) chromaticity diagram. The inner oval and the filled circle at coordinate (x,y) of (0.33, 0.33) indicate the white region and the ideal color, respectively. Note that PS and PVK denote polystyrene and poly (N-vinylcarbazole) film (reprint from ref. [91], Copyright 2005 Wiley-VCH)... 

The Newtonian viscosity of some polymers increases essentially linearly with the weight average molecular weight, and for other polymers the Newtonian viscosity increases with an exponential power of the molecular weight. The exponential power is found to be about 3.4, but this power does deviate for some polymers. These two transitions, Newtonian to pseudo-plastic and linear to 3.4 power in the Newtonian range are often related to molecular structure as demonstrated in Fig. 3.31 [22]. The polystyrene data used to develop the Adams-Campbell viscosity function showed almost no shear thinning at [18]. That is why the power law slope, s, is a function of and M. At the slope is zero and the material would be essentially Newtonian. 

In solution, block copolymers display interesting colloidal and interfacial properties. They can be used as emulsifying agents in water-oil and oil-oil systems (6 ). In the later case, the oil phases are solid and they give rise to polymeric alloys (7.) or they are liquid and they allow the preparation of latexes in organic medium (8 ). However, the molecular structure of block copolymers based on polybutadiene PB (70 ) and polystyrene PS behave as thermoplastic elastomers when engaged in multiblock (PB-PS)n or triblock (PS-PB-PS) structures but never when implied in inverse triblock or diblock arrangements. Similarly the... 

Gramain P, Borreill J (1978) Influence of molecular weight and molecular structure of polystyrenes on turbulent drag reduction Rheol Acta 17 303... 

Solution (S-SBR) consists of styrene butadiene copolymers prepared in solution. A wide range of styrene-butadiene ratios and molecular structures is possible. Copolymers with no chemically detectable blocks of polystyrene constitute a distinct class of solution SBRs and are most like slyrcnc-buladicne copolymers made by emulsion processes. Solution SBRs with terminal blocks of polystyrene (S-B-S) have the properties of self-cured elastomers. They are processed like thermoplastics and do not require vulcanization. Lithium alkyls are used as the catalyst. 

Conversion of styrene to polystyrene is an example of such molecular structure, which is repetitive and simple. Relatively little opportunity is offered to precisely control critical molecular design parameters. Although nanostructure dimensions can be attained, virtually no control over atom positions, covalent connectivity or shapes is possible. 

Figure 4.46. Molecular structures of commonly used OLED/PLED materials. Shown are (a) Alq3 (tris(quinoxalinato)Al (III)) used as an electron-transport material (b) DIQA (diisoamylquinacridone) used as an emissive dopant (c) BCP (2,9-dimethyl-4,7-diphenyl-l,10-phenanthroline) used as an exciton/ hole blocking agent (d) NPB (l,4-bis(l-napthylphenyl amino)biphenyl) (e) PFO (9,9-dioctylfluorene) used as an emissive polymer in PLEDs (f) PEDOT-PSS (poly-3,4-ethylenedioxythiophene-polystyrene sulfonate) used as a hole transport material in PLEDs.

Figure 5.1. Molecular structures of the chemical repeat units for common polymers. Shown are (a) polyethylene (PE), (b) poly(vinyl chloride) (PVC), (c) polytetrafluoroethylene (PTFE), (d) polypropylene (PP), (e) polyisobutylene (PIB), (f) polybutadiene (PBD), (g) c/5-polyisoprene (natural rubber), (h) traw5-polychloroprene (Neoprene rubber), (i) polystyrene (PS), (j) poly(vinyl acetate) (PVAc), (k) poly(methyl methacrylate) (PMMA), ( ) polycaprolactam (polyamide - nylon 6), (m) nylon 6,6, (n) poly(ethylene teraphthalate), (o) poly(dimethyl siloxane) (PDMS).

The polymer solution from the polymerization process contains the polystyrene in its final molecular structure and morphology. Additives, such as lubricants, stabilizers, etc., have frequently already been incorporated. 

As reported by Diehl et al. [58], interpolymers are also compatible with a broader range of polymers, including styrene block copolymers [59], poly(vinyl chloride) (PVC)-based polymers [60], poly(phenylene ethers) [61] and olefinic polymers such as ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and chlorinated polyethylene. Owing to their unique molecular structure, specific ESI have been demonstrated as effective blend compatibilizers for polystyrene-polyethylene blends [62,63]. The development of the miscibility/ compatibility behavior of ESI-ESI blends differing in styrene content will be highlighted below. 

The standard molecular structural parameters that one would like to control in block copolymer structures, especially in the context of polymeric nanostructures, are the relative size and nature of the blocks. The relative size implies the length of the block (or degree of polymerization, i.e., the number of monomer units contained within the block), while the nature of the block requires a slightly more elaborate description that includes its solubility characteristics, glass transition temperature (Tg), relative chain stiffness, etc. Using standard living polymerization methods, the size of the blocks is readily controlled by the ratio of the monomer concentration to that of the initiator. The relative sizes of the blocks can thus be easily fine-tuned very precisely to date the best control of these parameters in block copolymers is achieved using anionic polymerization. The nature of each block, on the other hand, is controlled by the selection of the monomer for instance, styrene would provide a relatively stiff (hard) block while isoprene would provide a soft one. This is a consequence of the very low Tg of polyisoprene compared to that of polystyrene, which in simplistic terms reflects the relative conformational stiffness of the polymer chain. 

FIGURE 1.2. Molecular structure of widely used it-conjugated and other polymers (a) poly(para-phenylene vinylene) (PPV) (b) a (solid line along backbone) and it ( clouds above and below the a line) electron probability densities in PPV (c) poly(2-methoxy-5-(2 -ethyl)-hexoxy-l,4-phenylene vinylene) (MEH-PPV) (d) polyaniline (PANI) (d.l) leucoemeraldine base (LEB), (d.2) emeraldine base (EB), (d.3) pernigraniline base (PNB) (e) poly(3,4-ethylene dioxy-2,4-thiophene)-polystyrene sulfonate (PEDOT-PSS) (f) poly(IV-vinyl carbazole) (PVK) (g) poly(methyl methacrylate) (PMMA) (h) methyl-bridged ladder-type poly(jf-phenylene) (m-LPPP) (i) poly(3-alkyl thiophenes) (P3ATs) (j) polyfluorenes (PFOs) (k) diphenyl-substituted frares -polyacetylenes (f-(CH)x) or poly (diphenyl acetylene) (PDPA). 

Lee and Char [93] studied the reinforcement of the interface between an amorphous polyamide (PA) and polystyrene with the addition of thin layers of a random copolymer of styrene-maleic anhydride (with 8% MA) sandwiched at the interface. After annealing above the Tg of PS, they found significantly higher values of Qc for samples prepared with thinner layers of SMA than for the thicker ones. They initially rationalized their results by invoking the competition between the reaction rate at the interface and the diffusion rate of the SMA away from the interface. For very thick layers, and therefore also for pure SMA, the reaction rate was much faster than the diffusion rate away from the interface and favored therefore a multiple stitching architecture, as shown schematically in Fig. 50. Such an interfacial molecular structure does not favor good entanglements with the homopolymer and is mechanically weak. 

The synthesis of homo- (Ti-Ti) and heterobinuclear (Ti-Zr) complexes linked by 1,2-G2H4 linker groups as shown in Scheme 316 has been reported. The molecular structures of the dimethylamido derivatives have been determined by X-ray diffraction methods. In the presence of binuclear borate activators, the methyl complexes produce long-chain branched polyethylene and polystyrene in homopolymerization reactions and ethylene-styrene co-polymers. The polymerization behavior differs from that obtained with the mononuclear compound (3-ethylindenylSiMe2-NBiOTiMea (Scheme 3 1 7).762"764... 

Brushes with diblock side chains have been prepared by the same concept as illustrated in Figure 13. In this case either a polystyrene block or a poly-(n-butylacrylate) block was grafted first by atom transfer polymerization, ATRP, on a poly(2-bro-mopropanoyl ethyl methacrylate), pBPEM, on which in a second step the other monomer was polymerized as the second block.189 Table 4 summarizes the molecular structure of the corresponding polymers, i.e., (i) the macroinitiator or mere backbone molecule (pPBEM) from which (ii) a brush with pnBuA homopolymer side chains (pBPEM-g—pnBuA), (iii) a... 

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