Chain transfer to solvent in the radical polymerization of N‐isopropylacrylamide

Abstract

Chain transfer to solvent has been investigated in the conventional radical polymerization and nitroxide‐mediated radical polymerization (NMP) of N‐isopropylacrylamide (NIPAM) in N,N‐dimethylformamide (DMF) at 120 °C. The extent of chain transfer to DMF can significantly impact the maximum attainable molecular weight in both systems. Based on a theoretical treatment, it has been shown that the same value of chain transfer to solvent constant, Ctr,S, in DMF at 120 °C (within experimental error) can account for experimental molecular weight data for both conventional radical polymerization and NMP under conditions where chain transfer to solvent is a significant end‐forming event. In NMP (and other controlled/living radical polymerization systems), chain transfer to solvent is manifested as the number‐average molecular weight (Mn) going through a maximum value with increasing monomer conversion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Chain transfer to solvent in the radical polymerization of structurally diverse acrylamide monomers using straight-chain and branched alcohols as solvents

“…In the case of a sufficiently high level of chain transfer to solvent, M n may go through a maximum with increasing conversion. [2] NMP of TBAM initiated by poly(t-BA)-SG1 was carried out in the three different alcohol solvents: 3-methyl-3-pentanol, 1-propanol, and 1-hexanol possessing a range of C tr,S (Table 1) can influence rate coefficients in radical polymerization [26] -in the case of NMP the situation would be complex as solvent effects may be expected on both the fundamental rate coefficients of propagation and termination, as well as the rate coefficients associated with the NMP equilibrium [3] -such a discussion goes beyond the scope of the present work. Suffice it to say that there is no correlation between R p and the C tr,S values.…”

Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide

“…To a solution of TIPNO-OH alkoxyamine 46 (0.6962 g, 1.961 mmol) and 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoyl chloride (1.001 g, 1.961 mmol) in 30 mL of anhydrous dichloromethane was added triethylamine (0.1997 g, 1.961 mmol) at room temperature. The reaction mixture was stirred for 1 hour, then 50 mL of dichloromethane and 50 mL of H 2 O were added.…”

“…6,7 It is particularly well-suited for heterogeneous radical polymerizations, since reagents such as the monomer, initiator and controlling agent are generally soluble in scCO 2 , but the resultant polymer is insoluble and precipitates. 2,3 If the precipitation system is carried out in the presence of a colloidal stabilizer to prevent coagulation of particles, then dispersion polymerization results giving polymer of narrow particle size a The monomer is not always soluble in the reaction medium, such as in the controlled/living nitroxide-mediated radical polymerization (NMP) of N-isopropylacrylamide (NIPAM) in scCO 2 , where an inverse suspension system is generated.…”

“…The performance of these fluorinated alkoxyamines in polymerizations of styrene in scCO 2 is compared with analogous polymerizations in solution, as well as, TIPNO and SG1-alkoxyamine 1a and 1d analogues. 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,, triethyl amine (Aldrich), ethylenediamine (Aldrich), Mn(OAc) 2 •4H 2 O (Acros Organics), pyridine (Acros Organics), (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henicosafluorododecyl), diisopropyl-silane (Fluorous Technologies Inc.), trifluoromethanesulfonic acid (TCI America), 1H, 1H, 2H, 2H-perfluorodecanol (Matrix Scientific), tetrabutylammoniumhydrogen sulfate (TCI America), 2-hydroxybenzaldehyde (EMD), and sodium hydroxide (Fisher Scientific) were used as received. Dichloromethane (Fisher Scientific) was dried over calcium hydride (Fisher Scientific) when anhydrous conditions were required.…”

“…[1][2][3] Advantages include a readily accessible critical point (31 °C and 7.4 MPa), 4 variable solubility by subtle changes in pressure and temperature, 5 and the lack of chain transfer to solvent in radical polymerizations. 6,7 It is particularly well-suited for heterogeneous radical polymerizations, since reagents such as the monomer, initiator and controlling agent are generally soluble in scCO 2 , but the resultant polymer is insoluble and precipitates. 2,3 If the precipitation system is carried out in the presence of a colloidal stabilizer to prevent coagulation of particles, then dispersion polymerization results giving polymer of narrow particle size distributions and well-defined particles (d ≈ 100 nm to 15 μm).…”