POLYMER DEPOSITION IN HAIR 547 • 30 • •o Figure 2. Effect of pH on the polymerization of methacrylamide in hair Although the dependence is similar to that obtained in the polymeri- zation of acrylonitrile in wool (8), the rate of deposition does not seem to be as much affected by increase in pH (up to 6). However, the extent of polymerization in the region of pH 5-6 depends primarily on the length of time during which THPC-treated hair is in contact with persulfate before the monomer is added. This interesting behavior is illustrated by Table VIII and will be discussed later. Table VIII Effect of Pcrsulfate on Polymerization of Methacrylamide in THPC-treated Hair a at 25øC IMAM] = 75 gl-• [K2S2Os] = 3 gl-• [THPC] = 3 gl-• time = 60 rain Time of Contact of THPC-treated Hair with Persulfate before Adding Monomer (min) Polymer Deposit at pH 2.2 6.0 •/3 63.5 36.3 15 ... 12.4 30 58.0 7.0 The hair was rinsed thoroughly for 30 min in running tap water after treatment with THPC.

548 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The results of polymerization experiments carried out at different liquor:hair ratios and various concentrations of persulfate are collected in Tables IX and X, respectively. The course of polymer deposition was investigated at various concen- trations of toohomer. The standard conditions of pretreatment were employed and the polymerization was carried out at a liquor:hair ratio of 50:1. The results obtained are given in Table XI and Fig. 3. Table IX Polymerization of Methaerylamide in THPC-treated Hair in 0.01N H2SO4 at 25øC and Different Liquor:Hair Ratios IMAM] = 50 gl-• [K•S•Os] = 3 gl-• time = 60 min Liquor: Hair Ratio Polymer Deposit (%) 5:1 5.8 10:1 15.3 20:1 37.1 50:1 51.0 100:1 57.2 Table X Effect of Persulfate Concentration on Rate of Polymerization of Methacrylamide ia THPC-treated Hair in 0.01N H•SO4 at 25øC and Liquor:Hair Ratio = 50:1 Polymer Deposit after [KaSaOs] g1-1 20 min 60 rain 1 18.5 36.8 3 23.0 50.2 6 32.1 53.3 12 35.5 55.0 Table XI Effect of Monomer Concentration on Polymerization of Methacrylamide in THPC-treated Hair in 0.01N H2SO4 at 25øC [K2$•O81 = 3 gl-• % Polymer Deposit after MAM] gl -• 6 min 15 min 30 min 45 min 60 min 25 ... 10.6 16.6 22.9 27.4 50 ... 21.1 35.7 43.7 49.8 75 ... 31.4 47.6 56.0 65.5 100 ... 42.1 62.3 76.1 85.5 200 40.1 65.8 86.2 97.5 113.8