Phenol reacts with formaldehyde to produce a linear polymer. Identify the polymer.

Novolac

The correct answer is option 3. Novolac.

When phenol reacts with formaldehyde under certain conditions, it produces different types of phenol-formaldehyde resins. These can be either linear or cross-linked polymers depending on the conditions of the reaction.

Novolac:

Phenol reacts with formaldehyde in the presence of an acid catalyst to produce Novolac. Novolac is a linear polymer that does not cross-link unless further treated with additional formaldehyde. Novolac is used in the production of molding powders, adhesives, and as a precursor to Bakelite.

Bakelite:

If the reaction between phenol and formaldehyde is conducted under basic conditions and with an excess of formaldehyde, it leads to a cross-linked, thermosetting polymer known as Bakelite. Bakelite is a three-dimensional network polymer.

Teflon: Teflon (polytetrafluoroethylene) is not related to phenol and formaldehyde; it is made from the polymerization of tetrafluoroethylene.

PMMA: PMMA (polymethyl methacrylate), also known as acrylic or Plexiglas, is made from the polymerization of methyl methacrylate.

Phenol reacts with formaldehyde to produce a linear polymer known as Novolac. Therefore, the correct answer is Novolac.