Charged IPNs

In simple homopolymers and networks, ionic charges may be introduced for a variety of reasons. For example, introducing about 5% of sodium methacrylic acid into polyethylene produces ionomers, which are clear, tough plastics. When the Tg of the polymer is below ambient, materials known as carboxylic rubbers are formed. Anionic and cationic ion exchange resins have been known for a long time.  

Three engineering uses have been proposed for ionic IPNs (1) cationic/anionic ion exchange resins, (2) piezodialysis membranes, and (3) thermoplastic IPNs. The last item is discussed briefly in Sections 5.7 and 8.7. The first two will be briefly treated here. 

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A. Effect of Different Compositions of PU/VMCC on the Mechanical Properties of Pseudo-IPN Coatings with and without Opposite Charge Groups... 

Figure 1. Effect of different compositions of PU/VMGC on the tensile strength of semi-IPN coatings with or without opposite charge groups.

The maximum tensile strength of the pseudo-IPNs appeared at about the 80 20 ratio of PU/VMCC for both pseudo-IPNs with and without opposite charge groups. Presumably the maximum entangle-ment between the VMCC chains and the PU network also occurred at this composition ( Figure 1). ... 

The maximum lap shear strength of the pseudo-IPNs, however, appeared at about the 75 25 composition for ionomer pseudo-IPNs with opposite charge groups and 70 30 composition for the pseudo-IPNs without opposite charge groups (Figure 2). 

As shown in Table 3, both pseudo-IPNs with and without opposite charge groups exhibited poor solvent... 

TABLE 2 IMPACT STRENGTH OF PSEUDO-IPN COATINGS FROM PU AND VMCC WITH AND WITHOUT CHARGE GROUPS... 

Figure Micrographs of semi-IPN with and without opposite charge groups by scanning electron microscopy (SEM),...

In contrast, the micrographs of the ionomer pseudo-IPN coatings with opposite charge groups. Figure U- (A-2 to C-2), did not reveal any phase separation. No white particles of the VMCC phase were visible in the dark matrix of the PU phase. Presumably the ionic bonds between the carboxyl and tertiary amine groups provided the best opportunity for interpenetration between the linear chains of VMCC and the networks of PU to prevent any possible phase separation from the ionomer pseudo-IPN microphase. The physical properties of ionomer... 

The miscibility between poly (vinyl chloride) and poly-urethanes based on poly (oxytetramethylene) glycol can be improved by introducing opposite charge groups to form ionic bonds. The improvement in miscibility from ionic bonds between the two polymer systems provided the best chance for interpene-tration between the linear chains of VMCC and the PU networks in order to obtain good physical properties of the ionomer pseudo-IPN coatings from PU and VMCC. 

Spectroscopic studies of the enzyme-substrate complex show that the 8-(L-a-aminoadipoyl)-L-cysteinyl-D-valine (ACV) thiolate coordinates to the metal center. First, there is a decrease in the Mossbauer isomer shift of the Fe(II) center from 1.2 to 1.0 mm/sec, indicating a more covalent Fe(II)-ligand environment [195], Second, an intense band appears at 390 nm in the visible spectrum of Cu(II)IPNS upon addition of ACV, which is associated with a thiolate-to-Cu(II) charge transfer transition found for tetragonal copper(II) centers [196], Last, EX-AFS analysis of the Fe(II)IPNS-ACV complex indicates the presence of a sulfur scatterer at ca. 2.3 A, which is a distance typical of Fe(II)-thiolate coordination [197,198], The very recently elucidated crystal structure of the Fe(II)IPNS-ACV complex confirms the thiolate coordination [199],... 

All latex IPN s were synthesized by two-stage emulsion polymerization techniques (1 18) as follows To 300 ml of deionized deaerated stirre 3 waTer at 60°C were added 50 ml of a 10% (W/V) solution of sodium lauryl sulfate followed by 5 ml of a 5% (w/V) solution of potassium persulfate. The calculated quantity of comonomer was added at a rate of about 2 ml per minute. When the first monomer was fully added a minimum of one hour was allowed to elapse. Then a new portion of initiator was added but no new soap followed by the second charge of comonomers under similar reaction conditions. 

CCD = charge-coupled device IHIs = interligand hypervalent interactions ILL = Institut Lane-Langevin INS = inelastic neutron scattering IPNS = intense pulsed neutron source LINAC = linear accelerator MaNDi=macro-molecular neutron diffractometer NiMH=nickel-metal OPAL = open pool Australian light-water reactor hydride SANS = small-angle neutron scattering SNS = spallation neutron source. 

Karmakar. B. and Ganguli, D., Effects of some variables on the point of zero charge of TiOj-ZrO, double oxides, Bull. Chem. Soc.. Ipn, 62, 1373, 1989. 

Experiments with IPN are performed with the hope that the reaction of its decomposition products with air would produce stronger reactive shock waves. Figure 7.4 shows the recorded pressure profiles. The amount of IPN in this case is stoichiometric, and the charge is initiated by gradual heating of the injector. 

In 1955, Solt discovered that IPNs with one network charged negatively and the other charged positively made superior ion exchange resins [Solt, 1955] see No.4. An important feature of these materials relates to having the two phases in juxtaposition on a very small scale. If the system is molecularly mixed, however, efficiency declines due to the interactions between the opposite polymer ions, ejecting the mobile salt ions. 

For a bound stationary state, the generalized Hellmann-Feynjiaan theorem is dEJdX =S ipn dH/dX) dr, where A is a parameter in the Hamiltonian. Taking A as a nuclear coordinate, we are led to the Hellmann-Feynman electrostatic theorem, which states that the force on a nucleus in a molecule is the sum of the electrostatic forces exerted by the other nuclei and the electron charge density. 

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