Functionalization of PPO

The composition of PPG—PEG blends has been determined using gpc with coupled density and RI detectors. PEG and PPG have different response factors for the density and RI detectors which were exploited (173). An hplc system with CHROMPAC RP-18C18 column at 298°C and acetonitrile—water or methanol—water as the mobile phase has been used to gather information about the functionality of PPO (174). 

Blends of PPO with PS or copolymers with 67.1 mole % or less pClS are compatible (i,.. one Tg) and show small S3mergistic maxima in modulus, strength, and elongation as a function of PPO composition. These maxima correspond to observed maxima in packing density as a result of specific interactions contributing to blend compatibility. 

Figure 5.11 Glass transition temperature of compatible blends of polystyrene and polyphenylene oxide (PPO) as a function of PPO content. Drawn after data from Bair (1970).

Figure 18.5b shows an example of the experimental y(r) function. The thickness of the crystalline phase <4> equals the intercept of the linear part of y(r) at the background level, and the long period L corresponds to the first maximum of y(r). The structural parameters obtained for SPS/PPO as a function of PPO content are given in Table 18.2. 

Though somewhat invalid, the calculation given under Preliminary Considerations illustrates the sensitive of the modulus to the precise functionality of the PPG. However, if the mole fraction of monohydroxy PPO in the PPG is considered, for illustration, to be 0.040 instead of 0.066, the calculated values of G ax, 104 >c, and 104Re for the LHT-240 elastomer are 0.318 MPa, 0.789, and 0.551, respectively. These values differ only slightly from those in Table III. Such results because, both p and P must become smaller with a decrease in the amount of monohydroxy PPO so that the calculated sol fraction will agree with that observed. 

Recent studies on PEO-PPO, PEO-PBO di- and triblock copolymers include the works of Bahadur et al. [121], who examined the role of various additives on the micellization behavior, of Guo et al. [122], who used FT-Raman spectroscopy to study the hydration and conformation as a function of temperature, of Booth and coworkers [ 123], who were mainly interested in PEO-PBO block copolymers with long PEO sequences, and of Hamley et al., who used in situ AFM measurements in water to characterize the morphology of PEO-PPO micelles [56,57]. 

Non-ionic polymers have also been blended with ionic block copolymers. Poly(vinyl phosphanate)-l7-polystyrene and PS-l -SPS have been blended with PPO. In both cases, improvements were seen in MeOH permeability over that of fhe unmodified block copolymers and conductivity values dropped as a function of increasing PPO confenf. PVDF has been blended wifh SEES in order fo improve its mechanical and chemical stability, but aggregation was found fo be a problem due fo incompafibility between components. However, it was found that a small amount (2 wt%) of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer as com-patibilizer not only led to greater homogeneity but also improved mechanical resistance, water management, and conductivity. ... 

PPO from tea reacts effectively with both 3 -4 and 3 -4 -5-hydroxylated catechins, with specificity for the o-diphenol (43,44). Studies defining the kinetics of PPO from tea in relation to substrate type are lacking as of this writing (ca 1997). Tea PPO has good functionality in the pH range 4.6—5.6 (43,45-48). 

The isothermal crystallization of PEO in a PEO-PMMA diblock was monitored by observation of the increase in radius of spherulites or the enthalpy of fusion as a function of time by Richardson etal. (1995). Comparative experiments were also made on blends of the two homopolymers. The block copolymer was observed to have a lower melting point and lower spherulitic growth rate compared to the blend with the same composition. The growth rates extracted from optical microscopy were interpreted in terms of the kinetic nucleation theory of Hoffman and co-workers (Hoffman and Miller 1989 Lauritzen and Hoffman 1960) (Section 5.3.3). The fold surface free energy obtained using this model (ere 2.5-3 kJ mol"1) was close to that obtained for PEO/PPO copolymers by Booth and co-workers (Ashman and Booth 1975 Ashman et al. 1975) using the Flory-Vrij theory. 

The dielectric relaxation of bulk mixtures of poly(2jS-di-methylphenylene oxide) and atactic polystyrene has been measured as a function of sample composition, frequency, and temperature. The results are compared with earlier dynamic mechanical and (differential scanning) calorimetric studies of the same samples. It is concluded that the polymers are miscible but probably not at a segmental level. A detailed analysis suggests that the particular samples investigated may be considered in terms of a continuous phase-dispersed phase concept, in which the former is a PS-rich and the latter a PPO-rich material, except for the sample containing 75% PPO-25% PS in which the converse is postulated. 

Figure 1. Dielectric loss of PPO as a function of temperature and frequency...

Figure 4. Dielectric loss of 50 PPO-50 PS mixture as functions of temperature...

Figure 5. Dielectric loss of 25 PPO-75 PPO mixture as functions of tempera-...

Figures 3-5 that the dielectric relaxation again reveals only a single a relaxation for the mixtures. These are, however, noticeably broader than the a relaxation of the pure polymers. The temperatures of the loss maxima, when plotted (Figure 7) as a function of wu the weight fraction of PPO in the mixtures, do not display the smooth monotonic increase in T0 vs. Wi that was shown by both the Vibron and the DSC results. Instead, there is a pronounced increase in Tg above = 0.5 to give a sigmoid curve for this relation. Some reservations should be attached to this observation inasmuch as data for only three polyblend compositions are available nevertheless a qualitatively similar phenomenon is observed in the analysis of the intensity of the y peak (below). Further, if only the stronger maxima in the dynamical mechanical data are considered— i.e.y if the secondary peaks and shoulders which led to the identification of two phases are omitted—then a similar sigmoid curve is found. The significance of this observation is discussed later.

Figure 6. Dynamical mechanical loss at 110 Hz for three PPO-PS mixtures as a function of temperature...

In Table I are presented functionalization level and d33 data for representative PPO-NPP films. Assuming approximate additivity of PPO... 

Figure 26.4B shows the calibration curve for PPO-B-immunosen-sors as a function of anti-CT concentrations. 

Figure4.3 Oxygen permeability coefficients of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) films of various thicknesses, as a function of aging time at 35 °C [52], Reproduced with permission of the American Chemical Society.

A thermohardening composition for glass fiber reinforced plastics consists of PPO, BPA/DC and a bismaleimide [45]. Still higher heat resistance is achieved, if the poly-functional maleimide, based on aniline-formaldehyde condensation products (Scheme 11), is used [46]. 

We turn to the results obtained with sample II, 10R5 (PPO-PEO-PPO). In Fig. 28 are shown the results for this sample (a) /7-F isotherms and (b) the static surface elasticity es as a function of F at three different temperatures. Relative to 77-F isotherms and the surface concentration F (equaling 0.4 mg/cm2) when es reaches es,max, there is no temperature dependence which is in complete contrast to those for sample I no temperature dependence can be discerned within experimental uncertainties in this case. 

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