ABSTRACT:Thermal and dynamic mechanical analyses of variously processed blends of poly(vinylidene fluoride) (PVF2) and poly(methyl methacrylate) (PMMA) were carried out to elucidate the effects of lower-critical-solution-temperature (LCST) behavior reported earlier by Paul on the morphologies and properties of this system. The two components are miscible in the blends with PVF2 content 4>w < 0.6. Such blends exhibit single glass transition at T;s, which follow the Gordon-Taylor scheme. On the other hand, the blends with c/Jw > 0.6, prepared by melt-mixing and annealing at 200oc for a sufficiently long period of time, exhibit two T.'s and two Tm's, implying a four-phase morphology. In such blends an LCST-type phase separation has taken place at a temperature as low as 200oc to give an amorphous mixture with 4>w 0.6 and a nearly pure PVF2 melt. Quenching of such melts leads to a four-phase morphology composed of a mixed amorphous phase with T. 55°C, an imperfect crystalline phase grown out from the mixture and hence having a low Tm, and a nearly pure semicrystalline PVF2 domains similar to form II crystals with -40oC and a higher Polymer blends of poly(vinylidene fluoride) (PVF2) and poly(methyl methacrylate) (PMMA) have been the subject of several recent studies. 1 -9 The general conclusion is that these components are miscible in the amorphous state, i.e., above the melting point of PVF2 l70°C). Below Tm the PVF 2 crystallizes from the melt, especially with high PVF2 content, ¢w, if the blend is kept above its glass-transition temperature, Tg. The blend forms a two-phase system consisting of a PVF 2 crystalline phase and a mixed amorphous phase. In short, this system is a typical example of a semicompatible polymer blend composed of a semicrystalline polymer and an amorphous polymer, in which phase t Present address: Research and Development Department, Bridges/one Tire Co., 2800-1 Ogawahigashimachi, Kodaira 187, Japan. separation occurs only by crystallization of the former. However, Paul et a/. 6 pointed out that this system exhibits lower-critical-solution-temperature (LCST) behavior with cloud points, TP, in a temperature range of about 330°C for blends with high ¢w· The TP are far above the ceiling temperature for PMMA Such an LCST behavior, if it really exists, might bring about additional complications to the phase-separation behavior and physical properties of PVF2/PMMA blends. If fact, there are certain discrepancies between reported Tg versus composition data for melt-mixed blends 2 • 5 and for solvent-cast blends 3 of this system. Thus, we have attempted to resolve these problems by comparing the thermal and dynamic mechanical behavior of melt blends with that of solvent-cast blends of this system. The results obtained are reported in this paper.

The copolymer of hydroxypropyl methacrylate (HPMA) and photochromic spiropyran methacrylate (SPMA) has been synthesized. The films of the copolymer (P(HPMA-SPMA)) in a hydrated state showed reversible swelling-shrinking behavior in response to photoreversible isomerization and metal complexation of SPMA units in spite of covalently noncross-linked copolymers. In addition, the protonated open form of the SPMA units of the copolymer was possibly stabilized thermodynamically by the HPMA units from ultraviolet-visible absorption measurement of the hydrated P (HPMA-SPMA) film. On the other hand, the difference in color of the hydrated films between P(HPMA-AABMA) and P (NIPMA-AABMA), which was a copolymer of N-isopropyl methacryl amide (NIPMA) and azobenzene methacrylate (AABMA) as a pH indicator, was suggestive of the interference of the proximal hydroxyl groups of the immobilized HPMA units with protonation of the AABMA units. The HPMA units of the copolymers also contributed to improvement of thermodynamic stability of the metal complexes with the SPMA units.

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