Branched phenol-formaldehyde oligomers

Novolacs are obtained by the reaction of phenol and formaldehyde in acidic conditions. Novolac oligomers are linear or slightly branched addition products linked by methylene bridges (molar masses in the range 500 5000 g mol-1). The reaction is usually carried out using a molar ratio CH20/ PhOH close to 0.8, to avoid gelation in the reactor (see Chapter 3) ... 

Much interest has centred on the branch of cyclophanes known as calixarenes. They are polyphenol systems that can act as hosts in the formation of inclusion compounds, where a small guest molecule resides completely in a cavity within a single host they are cone-shaped cavitands . Several accounts have appeared of their history. The discovery by Baeyer of a formaldehyde/phenol resin led to Bakelite and to the work of A. Zincke and E. Ziegler, who gave to the first oligomer a tetrameric structure of a calix[4]arene. Later syntheses by Gutsche (1978) led to calixarenes with 4, 6 or 8 phenol residues.107-109... 

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