Stabilizer molar mass

The effects of stabilizer molar mass have not often been studied. For use of PEOX to stabilize PMMA particles [21], a molar mass of 500 kg mol produced stable, monodisperse particles at lower concentration than 200 kg mol PEOX. For stabilization of polystyrene particles by HPC [29], it was the low viscosity (i.e. low molar mass) grade which gave the more stable dispersions. The predictions of Paine s grafting models were that the power law dependence of particle size on stabilizer molar mass would lie between the bounds -6 and (l-2d)/2, where b is the exponent relating the radius of gyration to molar mass. For PVP in methanol, h is 0.32 [43] and the predicted bounds are —0.32 to -H3.18. Figure 22.4, for PVP stabilization of PMMA particles in m anol [42], shows exponents of —0.25, —0.19 and —0.14 at 2, 4 and 6% PVP wdiich are closer to Paine s full adsorption model. 

Additional information on the possible processing, thermal stability, molar mass, type of filler, filler content, etc. are needed. All this detailed information is contained in the polymer materials designation code. The codes help in selection of a suitable polymer material. 

Chemical Grafting. Polymer chains which are soluble in the suspending Hquid may be grafted to the particle surface to provide steric stabilization. The most common technique is the reaction of an organic silyl chloride or an organic titanate with surface hydroxyl groups in a nonaqueous solvent. For typical interparticle potentials and a particle diameter of 10 p.m, steric stabilization can be provided by a soluble polymer layer having a thickness of - 10 nm. This can be provided by a polymer tail with a molar mass of 10 kg/mol (25) (see Dispersants). 

Solution reactions between diacid chlorides and diols or diphenols are carried out in THF or CH2C12 at —10 to 30°C in die presence of tertiary amines such as triethylamine or pyridine, which play a role of both reaction catalyst and HC1 acceptor (Scheme 2.26). This synthetic mediod is also termed acceptor-catalytic polyesterification.295-297 High-temperature solution reactions have also been reported for a number of less soluble, generally semicrystalline, aromatic polyesters.6 They yield high-molar-mass polyesters exhibiting good mechanical properties and thermal stability. 

Similarly, triphenylphosphine dichloride (TPPCI2) can activate aromatic carboxylic acids in pyridine through the formation of acyloxyphosphonium salts (Scheme 2.30).313 A side reaction between tire intermediate acyloxyphosphonium species and a second carboxyl endgroup leading to the formation of anhydrides has been reported.313 This chain-limiting reaction decreases tire molar mass, while the presence of anhydride linkages in tire chains adversely affects the thermal and hydrolytic stability of the final polyester. 

Empirical formula Molar mass Melting point Physical state/odor Vapor pressure Water solubility Specific gravity Stability Other properties... 

A review of the literature demonstrates some trends concerning the effect of the polymer backbone on the thermotropic behavior of side-chain liquid crystalline polymers. In comparison to low molar mass liquid crystals, the thermal stability of the mesophase increases upon polymerization (3,5,18). However, due to increasing viscosity as the degree of polymerization increases, structural rearrangements are slowed down. Perhaps this is why the isotropization temperature increases up to a critical value as the degree of polymerization increases (18). 

On well characterised non-stabilized PP samples [48] having molar mass within 45-180 kg/mol with differing tacticity and crystallinity, we can see that the increasing molar mass leads to an increase of induction time and reduction of the maximum chemiluminescence intensity (Figure 14). The polymer with higher average molar mass appears to be more stable than that with lower molar mass. This may be ascribed to the effect of increased concentration of more reactive terminal groups, which promote initiation of thermal oxidation. 

Because the presence of an electrolyte increases the dimensions of micelles and microemulsion droplets [115], it may be expected that in presence of ions the size of microgels is also increased. This expectation could be confirmed external electrolyte increases Mw (Fig. 21) as well as dz and [r ] (Fig. 22) up to the limit of the emulsion stability. Therefore, the addition of an external electrolyte to the reaction mixture for the ECP of EUP and comonomers is a means to vary the molar mass, the diameter and the intrinsic viscosity of microgels from EUP and comonomers deliberately. 

A low or high molar mass stabilizing component whenever the polymer matrix of choice does not exert a stabilizing effect on the trapped protein drug. 

Polyethylene glycol has been used as reducing and stabilizing agent for Au NPs. The stability of the resulting Au colloids and the reaction rates are dependent on polymer molar mass. The Au NPs are characterized using UV-Vis, analyzing the plasmon bands [108]. 

From thermodynamic investigations invaluable qualitative and quantitative information is provided with regard to the phase transitions and vicinity of transitions of polymers and conventional low molar mass liquid crystals. Furthermore they give information about the kind of transition and phase stability relations, which are necessary to test theories or to evaluate new theoretical considerations. Owing to... 

Anionic surfaces flat adsorption (DADMAC with low or moderate molar mass) partial adsorption (copolymers with low charge density, homo-and copolymers with high molar mass, branched structures) recharge of surfaces, neutralization, stabilization... 

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