“Glamorous polymer” experiment

How to make a polymer from a resorcinol-formaldehyde solution

Prac­ti­cal­ly all of the sub­stances around us are poly­mers These sub­stances are used in ma­chine build­ing, the tex­tile in­dus­try, agri­cul­ture, medicine, au­to­mo­bile and ship build­ing and air­craft con­struc­tion. Poly­mers are also used in ev­ery­day life, and are con­tained in tex­tile and leather items, crock­ery, glue and var­nish­es, jew­el­ry and oth­er items.

On the ba­sis of high molec­u­lar com­pounds, rub­bers, fibers, plas­tics, films, paints and coat­ings are made. Poly­mers are ob­tained by the re­ac­tion of poly­mer­iza­tion – the re­ac­tion of the for­ma­tion of a high molec­u­lar com­pound (a poly­mer) through the grad­u­al at­tach­ment of mol­e­cules of a low molec­u­lar sub­stance (a monomer). In our next ex­per­i­ment, we will show how the re­ac­tion of the poly­mer­iza­tion of re­sor­ci­nol and formalde­hyde in an acidic medi­um takes place.

Safe­ty pre­cau­tions

Wear rub­ber gloves and pro­tec­tive glass­es when con­duct­ing the ex­per­i­ment, as con­cen­trat­ed hy­drochlo­ric acid caus­es burns. Formalde­hyde and re­sor­ci­nol are tox­ic and car­cino­genic sub­stances – work with a fume hood or in a well-ven­ti­lat­ed room.

Warn­ing! Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.

Reagents and equip­ment:

  • 10% re­sor­ci­nol so­lu­tion;
  • 35% formalde­hyde so­lu­tion;
  • 35% hy­drochlo­ric acid;
  • beaker;
  • cu­vette.

Step-by-step in­struc­tions

The re­sor­ci­nol and formalde­hyde so­lu­tions are poured into a beaker. Then a few drops of con­cen­trat­ed hy­drochlo­ric acid are added, and the pale pink flakes of the poly­mer pre­cip­i­tate. In a few min­utes, the hy­drochlo­ric acid be­comes even­ly dis­trib­uted around the test tube, and the en­tire so­lu­tion poly­mer­izes to a red-pink sol­id poly­mer.

Pro­cess­es de­scrip­tion

When con­cen­trat­ed hy­drochlo­ric acid is added to a so­lu­tion of re­sor­ci­nol and formalde­hyde, a poly­mer­iza­tion re­ac­tion starts, in which the mol­e­cules of re­sor­ci­nol and formalde­hyde bond and form the long chain of a poly­mer.

C₆H₆O₂ + CH₂O + HCl → H-[СН₂-C₆H₄O₂]ₙ-C₆H₅O₂