Synthesis of high molecular weight five-arm star polymers by improved electrochemically mediated atom transfer radical polymerization

POLIMERY 2017, 62, nr 9 645 0 1 2 3 4 0.0 -0.4 -0.8 -1.2 -1.6 _{0.31 cm}-1 0.18 cm-1 0.06 cm-1 I, mA SW/V_tot: Polymerization time, h 0 40 80 120 160 0.0 0.2 0.4 0.6 0.8 1.0 1.2 ln( I0 /It ) Polymerization time, s 0 1 2 3 4 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Polymerization time, h ln([M ]0 /[M] )

Fig. 1. Effect of SW/V_tot ratio on the synthesis of glucose-based

star polymers shown as: a) current profile, b) first order plot of current, c) first order kinetic plot of monomer conversion

0 20 40 60 80 100 0 20 40 60 80 100 1.1 1.2 1.3 Monomer conversion, % M n · 10 -3 M w /M n

Fig. 2. Effect of SW/Vtot ratio on evolution of Mn and Mw/Mn

ver-sus monomer conversion during the synthesis of glucose-based

star polymers 0.3 0.4 0.5 0.6 0.5 0.6 0.7 0.8 0.9 1.0 R2 _{= 0.868} (SW/V_tot)1/2_{, cm}-1/2 ap p kp , h -1

Fig. 3. Effect of SW/V_tot ratio on apparent polymerization rate

coefficient (_kapp

p )

In this case R_p is defined as [39]:

R_p = k_p[M][P_n] = k_p[M] [X-CuII/L] t app red k k • ₍₂₎

where: [P_n•] _{– concentration of propagating radicals.}

The reduction of deactivator rate constant can be pre-sented as [38]: π       = Do V_tot SW app kred (3) The _kapp

p is proportional to the root of the reduction rate

constant [_kapp

red _{= ln(I}0/It)] [40] and, based on eq. (3), kpapp is

proportional to the square root of SW/V_tot.

The polymerization kinetics and linear molecular mass evolution with monomer conversion, illustrated in

Fig. 1c and Fig. 2, result in polymers with low M_w/M_n

val-ues (Fig. 4a–c). Furthermore, M_w/M_n were dependent on

SW, but still remained low, i.e., 1.14 at 87 % of monomer

conversion (SW/V_tot = 0.06 cm-1_{) (Fig. 4c).}

a)

b)