Propylene oxide polymer, effect

The stereoregularity—i.e., distribution of the stereosequence length in these polymers—has a marked effect on the crystallization rates and the morphology of the crystalline aggregates. These differences, in turn, influence the dynamic mechanical properties and the temperature dependence of the dynamic mechanical properties. In order to interpret any differences in the dynamic mechanical properties of polymers and copolymers of propylene oxide made with different catalysts, it was interesting to study the differences in the stereosequence length in the propylene oxide polymers made with a few representative catalysts. 

The stereosequence length also has a marked effect on the isothermal crystallization kinetics of the propylene oxide polymers. These studies and analysis of results on crystallization kinetics will be described in detail in another communication. Here we summarize briefly the main conclusions of the effect of stereosequence length on the isothermal crystallization rates. 

Figure 4. Effect of stereoregularity on texture of propylene oxide polymers at same degree of supercooling A T - 30° C. Sample A with long stereo sequence length sample C with short stereosequence length.

Table III. Effect of Stereo regularity on Crystallization Kinetics of Propylene Oxide Polymers...

Moacanin, j., and E. F. Cuddihy Effect of Polar Forces on the Viscoelastic Properties of Poly(Propylene Oxide). Polymer Preprints 6, No. 2, 799—806 (1965). 

A number of catalyst systems have been developed (2 fL>A which result In propylene oxide polymers of different stereosequence distribution. In the following, we review some of our work on the characterization of stereosequence length In propylene oxide polymers prepared with different catalysts, and more importantly, studies on the effect of the differences in stereose-sequence length on the crystallization behavior and mechanical properties of the polymers. 

The effect of stereosequence distribution on crystallization kinetics Is dramatic. We have previously reported our studies on the Important effects of stereosequence length on crystallization kinetics and morphology of propylene oxide polymers (22). Here we summarize the main conclusions of this study, so that results on the time-temperature dependence of mechanical response may be fully appreciated In the light of these conclusions. 

Ethylene oxide (qv), propylene oxide (qv), butylene oxide, and other epoxides react with ethanol to give a variety of Uquid, viscous, semiwax, and soUd products. These products are used ia the coatings iadustry as solvents, and as paints, antioxidants, corrosion inhibitors, and special-purpose polymers. Recent concerns about the health effects of ethanol containing glycol ethers have led to the decline in the production of these compounds. 

In most cases the catalytically active metal complex moiety is attached to a polymer carrying tertiary phosphine units. Such phosphinated polymers can be prepared from well-known water soluble polymers such as poly(ethyleneimine), poly(acryhc acid) [90,91] or polyethers [92] (see also Chapter 2). The solubility of these catalysts is often pH-dependent [90,91,93] so they can be separated from the reaction mixture by proper manipulation of the pH. Some polymers, such as the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers, have inverse temperature dependent solubihty in water and retain this property after functionahzation with PPh2 and subsequent complexation with rhodium(I). The effect of temperature was demonstrated in the hydrogenation of aqueous allyl alcohol, which proceeded rapidly at 0 °C but stopped completely at 40 °C at which temperature the catalyst precipitated hydrogenation resumed by coohng the solution to 0 °C [92]. Such smart catalysts may have special value in regulating the rate of strongly exothermic catalytic reactions. 

The influence of the solvent on chiroptical properties of synthetic polymers is dramatically illustrated in the case of poly (propylene oxide). Price and Osgan had already shown, in their first article, that this polymer presents optical activity of opposite sign when dissolved in CHCI3 or in benzene (78). The hypothesis of a conformational transition similar to the helix-coil transition of polypeptides was rejected because the optical activity varies linearly with the content of the two components in the mixture of solvents. Chiellini observed that the ORD curves in several solvents show a maximum around 235 nm, which should not be attributed to a Cotton effect and which was interpreted by a two-term Drude equation. He emphasized the influence of solvation on the position of the conformational equilibrium (383). In turn, Furakawa, as the result of an investigation in 35 different solvents, focused on the polarizability change of methyl and methylene groups in the polymer due to the formation of a contact complex with aromatic solvents (384). 

Sakai T, Alexandridis P (2005) Spontaneous Formation of Gold Nanoparticles in Poly(ethylene oxide)-Poly(propylene oxide) Solutions Solvent Quality and Polymer Structure Effects. Langmuir 21 8019-8025... 

The first enantiomer-selective polymerization was performed with propylene oxide (172) as a monomer [245], The polymerization was carried out with a ZnEt2/(+)-bor-neol or ZnEt2/(-)-menthol initiator system. The obtained polymer was optically active and the unreacted monomer was rich in (S)-isomer. Various examples are known concerning the polymerization and copolymerization of 172 [246-251 ]. A Schiff base complex 173 has been shown to be an effective catalyst In the polymerization at 60°C, the enantiopurity of the remaining monomer was 9% ee at 50% monomer conversion [250],... 

The aluminium alkyls and alkoxides were found to be effective also in the polymerization of ethylene oxide and phenyl glycidyl ether the latter gave considerable amounts of low molecular weight, crystalline polymer. Aluminum triethyl was examined by Kambaka and Hatano (38) in the polymerization of several cyclic ethers and found to be fairly effective for propylene oxide and 2-methyl-oxacyclobutane but not for oxacyclobutane and tetrahydrofuran. The combination of zinc diethyl and alumina gave a high rate of polymerization with ethylene or propylene oxide (39). 

The first report on the coordination polymerisation of epoxide, leading to a stereoregular (isotactic) polymer, concerned the polymerisation of propylene oxide in the presence of a ferric chloride-propylene oxide catalyst the respective patent appeared in 1955 [13]. In this catalyst, which is referred to as the Pruitt Baggett adduct of the general formula Cl(C3H60)vFe(Cl)(0C3H6),CI, two substituents of the alcoholate type formed by the addition of propylene oxide to Fe Cl bonds and one chlorine atom at the iron atom are present [14]. A few years later, various types of catalyst effective for stereoselective polymerisation of propylene oxide were found and developed aluminium isopropoxide-zinc chloride [15], dialkylzinc-water [16], dialkylzinc alcohol [16], trialkylalumi-nium water [17] and trialkylaluminium-water acetylacetone [18] and trialkyla-luminium lanthanide triacetylacetonate H20 [19]. Other important catalysts for the stereoselective polymerisation of propylene oxide, such as bimetallic /1-oxoalkoxides of the [(R0)2A10]2Zn type, were obtained by condensation of zinc acetate with aluminium isopropoxide in a 1 2 molar ratio of reactants [20-22]. 

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