Facile Synthesis of Tertiary Amine Pendant Polymers by Cu⁰-Mediated ATRP under Aqueous Conditions

Abstract

Cu 0 -mediated atom transfer radical polymerization (ATRP) in aqueous media is extended to tertiary amine-pendant methacrylate polymers with poly([2-dimethylamino]ethyl methacrylate) (PDMAEMA) serving as a model polymer. By increasing the concentration of deactivating Cu II species, reducing the reaction temperature, and increasing the supporting halide concentration to 1 M, polymers with well-defined molecular weight distributions (MWDs) are achieved in under 4 h. MWDs show good agreement with theoretical values, with polydispersity indices (Đ) as low as 1.14. Furthermore, this reaction system shows a remarkable tolerance to dissolved oxygen, with little to no deleterious effects observed for polymerizations run without degassing prior to initiation. Syntheses at a mildly acidic pH of 3.5 demonstrate excellent retention of active end groups as demonstrated by chain extensions at near-quantitative conversion and extend the system to 2-(diethylamino)ethyl methacrylate (DEAEMA) and 2-(diisopropyl)ethyl methacrylate (DPAEMA). This work presents a new aqueous method for the rapid and facile synthesis of tertiary amine-pendant polymers with well-defined MWDs.

Solution and Film Self-Assembly Behavior of a Block Copolymer Composed of a Poly(ionic Liquid) and a Stimuli-Responsive Weak Polyelectrolyte

“…PDMAEMA was selected as it has a weak tertiary amine pendant group that can be protonated at pH values lower than ∼7.5 (pK a ∼7 to 8) to form cationic charge groups. 34,37,38 Further, PDMAEMA has been previously found to display material property changes in response to pH and salt. 39,40 An imidazolium-based PIL with a styrenic polymer backbone was selected as it has been successfully polymerized by ATRP methods previously.…”

“…The macroinitiator was synthesized using an aqueous-based Cu(0)-mediated ATRP procedure recently reported by the authors' group. 34 Figure 2 shows the kinetic results for the macroinitiator synthesis in aqueous solution. The PDMAEMA displayed pseudo-first-order kinetics as demonstrated by the linear increase in ln[M] o /[M] with time (Figure 2a) with a final monomer conversion of ∼70%.…”

“…61 These peaks are typical for tertiary amine salts, which indicates at least partial protonation of the tertiary amine group in the block copolymer after synthesis. As the PDMAEMA was synthesized in pH ∼ 8.6 conditions, the protonation likely results from a drop in pH to below the pK a of PDMAEMA (pK a ∼ 7 to 8) 34,38 during the purification step on precipitation with ammonium sulfate. 62 Below 1800 cm −1 , the C�O ester stretch at ∼1728 cm −1 from the PDMAEMA block is observed in the block copolymer sample 63 (Figure 4b).…”

“…Cu(0)-mediated ATRP is a controlled polymerization technique that uses a zero-valence metal to in situ produce the Cu(I) activating species through comproportionation, which then mediates the monomer addition to the polymer chain backbone in a controlled manner. − ATRP is characterized by pseudo-first-order kinetics as determined by a linear ln[ M ] o /[ M ] plot with time, where M o and M are the monomer concentration initially and at time, t , respectively. ATRP also allows for predicting the degree of polymerization (DP) and the number-average molecular weight ( M n ) based on the starting monomer ( M o ) and initiator ( I o ) concentrations and conversion (χ) and monomer molecular weight (MW monomer ): DP theo = false[ M false] normalo false[ I false] normalo χ M normaln theo = DP ( MW monomer ) This method generally produces narrow polydispersity indices (ratio of weight-average molecular weight, M w , to number-average molecular weight, M n , PDI = M w / M n ) of less than ≤1.5 for polyelectrolytes. , …”

Study on the Interaction of Plasma-Polymerized Hydrogel Coatings with Aqueous Solutions of Different pH

“…For all d-HD coatings investigated, it can be seen that the polar component decreases with increasing pH ( Figure 6 ). At pH 4, the tertiary amine groups of DEAEMA are protonated, leading to an electrostatic repulsion of the positive charges, which results in a stretched, flexible conformation of the HD14 coating ( Figure 7 ) [ 45 , 46 , 47 ].…”