Abstract
High molecular weight novolaks were prepared by polycondensation of phenol with paraformaldehyde in acetic acid. The novolak contains soluble, high molecular weight fractions (M w ≥ 10 6 ). The Θ-temperature of the acetylated novolak was determined in 2-ethoxyethanol according to the Shultz-Flory method. The solution viscosity of acetylated and deacetylated novolaks in THF at 25 C and in a Θ-solvent (2-ethoxyethanol at 105°C) was measured, and the molecular dimension in solution was estimated from the parameters of the Mark-Houwink-Sakurada equation. The exponent of 0.24 in THF (good solvent) for acetylated novolak is equal to that in the Θ-solvent. This suggests that the conformation of the novolak is compact like a sphere both in the good and the Θ-solvent. The theoretical value of the exponent in the MHS equation for highly branched polymers is between 0.2 and 0.25 in a Θ-solvent. The exponent for acetylated novolak in the Θ-solvent is close to this value. It is suggested that the acetylated novolak behaves like a highly branched polymer in a Θ-solvent. The 13 C NMR spectrum of novolak confirms that the novolak molecule is a highly branched polymer.
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