Small s method

Table 3. Solubility Parameters of Acrylic Homopolymers Calculated by Small s Method ...

Data obtained by Small s method expect for that of Saniicizec 8 which was estimated from boiling point measurements. 

While these equations are crude approximations describing the actual behaviors of various polymeric systems, they have widespread experimental viability [123]. These equations assume that the systems are thermodynamically miscible and stable. Equations resolving the solubility parameters of mixtures can also be done using Small s or Fedors methods [124,125]. This latter method only requires the knowledge of the structural formula of the compounds whereas Small s method requires experimental determination of the molar volume. 

The solubility parameter of the compounds, whose structural formula is known, can be calculated by Small s method based on the supposition that cohesive forces of separate atomic groups and radicals entering the composition of a low-molecular-weight substance or an elementary section of a macromolecule exert an additive effect. The respective calculations make use of the so-called molecular attraction constant F, whose values for different functional groups are cited in special literature [74]. These constants are related with solubility parameter 5... 

Small s method reeeived the greatest interest. Small has used the data of Seatehard showing that the square root of a produet of eohesion energy of substanee and its volume is a linear funetion of a number of earbon atoms in a moleeule of substanee. He also proposed additive eonstants for various groups of organie moleeules that permit ealeulation of (EV)" value. He named these eonstants as molar attraetion eonstants, Fj ... 

Small s method is the most widespread. Srrtall rrsed adrlitive constants for the various groups in organic molecules. These constants are known as molar attraction constants ... 

Another useful tool is the Hildebrand solubility theory, which is applicable to apolar and moderately polar systems. For strongly polar systems, it is unable to correctly qualify the compatibility between components. However, the massive amount of interaction parameters data obtained in recent decades, and mainly Small s method, allowing to assess them, make this method quite efficient and readily applicable. The Hildebrand solubility parameter, 5, can be defined as the square root of the cohesive energy density (CED) and it is measured in (MJ m )° . This parameter indicates the polarity level of the component and goes from 12 (MJ m )° for nonpolar components to 23 (MJ m )° for water. The larger the difference... 

Askadski et al. (1977) have proposed a procedure to calculate the CED of LMWL and polymers in terms of the molecule packing coefficients. These values match tho.se calculated by means of Small s method in the case of simple non-polar liquids and are closer to the experimental ones for more complex (polar and with 11-bonds) liquids. 

Small s method received the greatest irrterest. Srrtall has used the data of Scatchard showing that the square root of a product of cohesion energy of snbstance and its volrrme is a linear function of a number of carbon atorrrs in a molecule of substance. He also proposed additive constants for various groups of orgarric molecules that permit calculation of (EV) value. He named these constants as molar attraction corrstants, Fj ... 

---