Copolymer quenching

Figure 9 Room temperature variation of peak 20ha o for ethylene 1-decene copolymers quenched (q) and annealed at room temperature (an). The value for the linear polymer is also given.

Porous films obtained from P(AdSt-FMA) and P(AMSt-FMA) [90] reached low porosities of approximately 25%, average pore diameters of approximately 20 nm, and a remailcable thermal stability of the porous structure up to 200°C. In this case saturation pressures between 7.5 and lOMPa and temperatures from -20 to 60°C were used following the depressurization process previously explained for other PS-based copolymers (quenching and slow depressurization). 

Crystallization of a semicrystalline block copolymer quenched from the melt will also be briefly reviewed. Chu and Hsiao [68] comprehensively reviewed recent developments in SAXS where they discussed simultaneous measurements with other techniques. Among recently developed techniques, we will focus on simultaneous SAXSAVAXS (wide-angle X-ray scattering) and/or Hv-SALS (depolarized small-angle light scattering) measurements [69,70] because these are powerful techniques to study crystallization and spherulitic higher-order hierarchical structures in semicrystalline block polymers [71,72]. Current developments will also be reviewed later in the subsection on semicrystalline block polymers. 

INFLUENCE OF MELT MICRODOMAINS ON CRYSTALLIZATION IN SEMICRYSTALLINE BLOCK COPOLYMERS QUENCHED FROM THE MELT... 

Figure 3. AFM phase images of the melt morphology of olefin block copolymers quenched from 160 °C (a) H31 and (b) H84... 

Fraaije, J.G.E.M., Van Vlimmeren, B.A.C., Maurits, N.M., Postma, M., Evers, O.A., Hoffmann, C., Altevogt, P., Goldbeck-Wood, G. The dynamic mean-field density functional method and its application to the mesoscopic dynamics of quenched block copolymer melts. J. Chem. Phys. 106 (1997) 4260-4269. 

Copolymer film is produced by extmsion blowing foUowed by water quenching. In-line, the film is blown, crystallized, and oriented. PVDC copolymer film is difficult to produce. 

The maximum rates of crystallisation of the more common crystalline copolymers occur at 80—120°C. In many cases, these copolymers have broad composition distributions containing both fractions of high VDC content that crystallise rapidly and other fractions that do not crystallise at all. Poly(vinyhdene chloride) probably crystallises at a maximum rate at 140—150°C, but the process is difficult to foUow because of severe polymer degradation. The copolymers may remain amorphous for a considerable period of time if quenched to room temperature. The induction time before the onset of crystallisation depends on both the type and amount of comonomer PVDC crystallises within minutes at 25°C. 

Extrusion Resins. Extmsion of VDC—VC copolymers is the main fabrication technique for filaments, films, rods, and tubing or pipe, and involves the same concerns for thermal degradation, streamlined flow, and noncatalytic materials of constmction as described for injection-molding resins (84,122). The plastic leaves the extmsion die in a completely amorphous condition and is maintained in this state by quenching in a water bath to about 10°C, thereby inhibiting recrystallization. In this state, the plastic is soft, weak, and pHable. If it is allowed to remain at room temperature, it hardens gradually and recrystallizes partially at a slow rate with a random crystal arrangement. Heat treatment can be used to recrystallize at controlled rates. 

The copolymers are used in the manufacture of filaments. These may be extruded from steam-heated extruders with a screw compression ratio of 5 1 and a length/diameter of 10 1. The filaments are extruded downwards (about 40 at a time) into a quench bath and then round drawing rollers which cause a three- to four-fold extension of the filaments and an increase in strength from about 10000 to 36 000 Ibf/in (70-250 MPa). The filaments are used for deck chair fabrics, car... 

Figure 11 shows Stern-Volmer plots for fluorescence quenching of the amphiphilic cationic copolymer QPh-x [74]. The quenching of QPh-x with MV2+ is expected to be much less effective than that of APh-x. The quenching data for the QPh-x system are presented in Table 3. For comparison, the data for a related... 

Similar data were reported by Turro et al., [62,63] who synthesized a copolymer of AA with 1.5 mol% of 2-[4-(l-pyrene)butanoyl]aminopropenoic acid, 19 and studied the fluorescence quenching with Tl +, Cu2+, and 1 ions in aqueous solution. 

Kaneko et al. [80, 81] prepared copolymers of AA (93.9-95.9 mol%) and vinylbipyridine (1.6-3.7 mol%) with pendant Ru(bpy)2+ (2.4-2.5 mol%) (25). The quenching of the excited state of the pendant Ru(II) complex by MV2+ was accelerated in alkaline aqueous solution owing to the electrostatic attraction of the cationic quencher. Interestingly, the quenching efficiency was dependent on the molecular weight of 25. The quenching of the polymer with MW 2100 occurred... 

Blends of EMA copolymer and EPDM containing vinyl norborene as a third monomer were also investigated. Blending was carried out at 180°C at a rotor speed of 100 rpm. After the reaction, the blends were quenched on the cold rolls and were sheeted out. They were examined by IR spectra. The reduction of peak area related to unsaturation indicated a progressive loss of EPDM due to reaction with EMA. The extent of reaction depended on the utilization of unsaturation which is estimated to be 14% for EMA/EPDM at a 70 30 ratio and 53% at a 50 50 blend ratio. The tensile properties exhibit synergism as the EMA proportions change from 0% to 50%. 

A porphinatoaluminum alkoxide is reported to be a superior initiator of c-caprolactone polymerization (44,45). A living polymer with a narrow molecular weight distribution (M /Mjj = 1.08) is ob-tmned under conditions of high conversion, in part because steric hindrance at the catalyst site reduces intra- and intermolecular transesterification. Treatment with alcohols does not quench the catalytic activity although methanol serves as a coinitiator in the presence of the aluminum species. The immortal nature of the system has been demonstrated by preparation of an AB block copolymer with ethylene oxide. The order of reactivity is e-lactone > p-lactone. 

The observed luminescence properties of the copolymer yarns can be easily explained if an energy transfer mechanism is assumed to be operating (Figure 7). Triplet-triplet energy transfer from the terephthalate units to the 4,4 -biphenyl -dicarboxyl ate units explains both the dual fluorescent/phospho-rescent emissions from the 4,4 -biphenyldicarboxyl ate units as well as the quenched phosphorescence from the terephthalate units. 

We will then examine other flexible polymer crystallization instances which may be interpreted, at least qualitatively, in terms of the bundle model. We will concentrate on crystallization occurring through metastable mesophases which develop by quenching polymers like isotactic polypropylene, syndiotactic polypropylene etc. In principle also hexagonal crystallization of highly defective polymers, and order developing in some microphase-separated copolymer systems could be discussed in a similar perspective but these two areas will be treated in future work. A comparison between the bundle approach and pertinent results of selected molecular simulation approaches follows. 

The DSC thermograms of several triblock copolymers and homopolymer HB are coiq>ared to that of a low density polyethylene in Figure 2. The thermograms are those of the first run on quenched samples. Their behavior is similar except that the temperature of the maximum in the DSC melting peak, Tm, for LDPE (110 C) is higher than that of HB (102°C). The depression of the melting point brought about by the presence of 5 to 8 mole percent... 

Figure 9. Comparison of stress-strain properties of the press-quenched films of HIBI block copolymers to those of homopolymer HB. Butadiene content is next...

Figure 15A. Temperature dependence of E at 110 Hz. Effect of variation in composition on properties of triblock copolymers on H1B1 as compared to those of HB. All films are press-quenched.

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