Poly with isotactic polystyrene

After having studied in our laboratory, polymer blends of amorphous polymers poly-c-caprolactone and poly (vinyl chloride) (1,2) (PCL/ PVC), blends with a crystalline component PCL/PVC (3,4), poly(2,6-dimethyl phenylene oxide) (PPO) with isotactic polystyrene (i-PS) (5) and atactic polystyrene (a-PS) with i-PS (6), we have now become involved in the study of a blend in which both polymers crystallize. The system chosen is the poly(1,4-butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blend. The crystallization behavior of PBT has been studied extensively in our laboratory (7,8) this polymer has a... 

Figure 2.10 Maps of conformational energy of various isotactic polymers as function of backbone torsion angles 0i and 02 (a) Isotactic polystyrene, (b) polypropylene, (c) poly(l-butene), and (d) poly(4-methyl-l-pentene). Succession of torsion angles. .. 0i020i02 [s(M/N) symmetry] has been assumed. Isoenergetic curves are reported every 10 (a,c,d) or 5 (b) kJ/mol of monomeric units with respect to absolute minimum of each map assumed as zero.

In the crystal structures of many other isotactic polymers, with chains in threefold or fourfold helical conformations, disorder in the up/down positioning of the chains is present. Typical examples are isotactic polystyrene,34,179 isotactic poly(l-butene),35 and isotactic poly(4-methyl-l-pentene).39,40,153,247... 

Fig. 64. Correlation of Gue-net s a (for atactic) and a (for isotactic polystyrene) with the adsorption parameter a, determined for the corresponding liquid with respect to poly(Sty-eo-DVB)...

A first approach to investigating the origin of hypochromism at 269.5 nm in styrene-methyl methacrylate random copolymers is based on its similarity to the hypochromism of isotactic polystyrene as compared with the atactic poly-... 

FIGURE 12.6 Plot of the glass transition temperature as a function of log r, where x is the number of chain atoms or bonds in the backbone. Data for (-0-) poly(a-methyl styrene), (-A-) poly(methyl methacrylate) (- -) polystyrene, (- -) poly(vinylchloride), (-A-) isotactic poly-propylene, (- -) atactic polypropylene, and (- -) poly(dimethylsiloxane). (From Cowie, J.M.G., Eur. Polym. J., 11, 297, 1975. With permission of Pergamon Press.)... 

As shown in Fig. 1, gelation may be also driven by phase transitions as for instance crystallization. Under specific conditions, formation of crystals from a homogeneous solution can give rise to junctions and then to a gel. This happens, for example, with poly(vinyl chloride) [15], isotactic polystyrene, polyethylene [15, 26-31], and many other polymers [32]. In these gels, the junctions are constituted... 

In addition to the studies mentioned above, there has been a number of reports on GPC of specific polymers amongst these are studies of short-chain polyethylene, polyethylenes, isotactic polystyrene, cellulose nitrate, and polysiloxanes. Slagowski et have reported GPC of poly(tetramethylene terephthalate) in hexafluoroisopropanol and Paschle et show that a mixture of small amounts of nitrobenzene with tetrachlorethane is a useful solvent for GPC of poly(ethyIene terephthalate). 

Fig. 2.2 DSC thermogram of pure isotactic polystyrene crystallized at 175 °C for 1 h. An exotherm feature appears between peak II and peak III (Scanning rate 1.25 °C/min). Adapted with permission from figure 3 in Plans J, MacKnight WJ and Karasz FE, Equilibrium Melting Point Depression for Blends of Isotactic Polystyrene with Poly(2,6-dimethylphenylene oxide). Macromolecules 17 810-814. Copyright (1984) American Chemical Society...

Numerous attesnpts have been made to predict the effectiveness of potential nxacleating agents with particular attention having been paid to the crystallisation of isotactic polypropylene, isotactic polystyrene (6), polyethylene (2 9) ard poly(ethylene terephthalate) (10,11). However, little can be concluded about the fundamental mechanism of heterogeneous nucleation, or the propeirties of effective nucleating agents. 

Categorize the following polymers with regard to their low-temperature physical structure polyethylene isotactic polypropylene poly (ethylene terephthalate) isotactic polystyrene atactic polystyrene atactic poly(vinyl alcohol) atactic poly(vinyl acetate) poly(ethylene-sfflf-propylene) with 50/50 molar composition, and the same polymer but with molar composition 98/2. 

Figures 3 and 4 compare the 300 MHz spectra of isotactic poly(butene-l) and isotactic polystyrene with the spectra of partially deuterated analogs. The resonances of methine, methylene and methyl protons are adequately resolved in these spectra. An AB pattern is observed for the methylene proton resonances in Figure 3A, as expected, but is barely evident in Figure 4C, due to the fact that the methylene protons in polystyrene have very similar shifts.

In miscible binary blends, amorphous homopolymers are completely accommodated within amorphous layers of the lamellar morphology formed after the crystallization of crystalline homopolymers. Stein et al. [51], for example, observed the lamellar morphology formed in a miscible blend of PCL and poly(vinyl chloride) (PVC) using SAXS as a function of composition. They found that PVC existed in amorphous layers of the lamellar morphology to yield a linear increase in the amorphous layer thickness with increasing PVC composition, whereas the crystalline layer thickness remained constant irrespective of composition. Wenig et al. [52] obtained similar results for a miscible blend of poly(2,6-dimethylphenylene oxide) (PPO) and isotactic polystyrene (iPS). However, a different result was reported for a miscible blend of iPS and atactic polystyrene [53], where the amorphous layer thickness was almost constant irrespective of composition. Stein et al. [51] explained this difference in... 

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