Dithiol-yne Polymerization: Comb Polymers with Poly(ethylene glycol) Side chains

Abstract

Recently dithiol-yne click chemistry and its role in the formation of cross-linked polymer networks and postpolymerization functionalizations has been studied; however, no research has considered this technique to form comb polymers with regular side chains. Here we report the first example of a grafted-through stepgrowth comb polymer via the utilization of dithiol-yne "click chemistry". First, we exhibited the efficacy of this reaction to produce modest-molecular-weight combs (M n = 16 kDa). Second, we displayed the ability to precisely control the length of the side chains of these combs along with the space between the side chains by using various molecular weights of propargylated PEG chains and a variety of alkanedithiol backbone spacers. The primary species of these reactions were macrocyclic comb polymers, with a smaller amount of dithiol-terminated comb polymers.

Crystallization-Induced Self-Assembly of Poly(ethylene glycol) Side Chains in Dithiol–yne-Based Comb Polymers: Side Chain Spacing and Molecular Weight Effects

“…Chemical structure of dithiol–yne-based comb polymers with several alkanedithiol spacers ( m = 4 and 10) and PEG side chains (0.8, 2.2, and 5.1 kg/mol) [for more details on the synthesis and chemical characterization, see ref ].…”

“…However, in all cases, the distance between two neighboring PEG side chains is kept constant since this is defined by the spacer, having 4 or 10 methylene groups (Figure ), depending on the sample. A detailed description of the synthesis and chemical characterization of the comb polymers used in this work can be found in a previous ref .…”

“…PEG homopolymers with one propargyl end group and several molar masses were synthesized. Then, comb polymers, constituted by a dithiol−yne-based ring polymer backbone and PEG side chains (see Figure 3), were obtained following the procedure reported before 8 and summarized in the Supporting Information (SI). PEG homopolymers (without propargyl end group) were used for comparison purposes with number-averaged molecular weights of 0.8, 2.2, and 5.1 kg/mol (determined by GPC).…”

“…It has been shown that the branch point distribution along the chain affects, among others, the rheological properties in low graft density comb polymers, broadening the relaxation time. Thus, designing synthetic methods to control the space between side chains is desirable to have well-defined properties, but it remains challenging. , Recently, a new strategy to synthesize comb polymers with precise control of the length of the side chains and the space between side chains has been reported by Curole et al, employing dithiol–yne “click chemistry” to obtain polythioether macrocycles based on several alkanedithiol backbone spacers. With this technique, novel macrocyclic comb polymers with PEG side chains have been synthesized.…”

Unsaturated sulfur-containing polymers from modular alcohol click chemistry

“…An effective method for synthesizing sulfur-containing polymers is through the Michael addition of thiols and alkynes. [1][2][3][4][5][6][7][8][9][10][11][12] For example, functional hyperbranched polymers of prop-2-ynyl-3mercaptopropanoate have been prepared by photo-initiated thiol-yne click polymerization under the assistance of the initiator of 2,2-dimethoxy-2-phenylacetophenone (DMPA), 13 and linear main chain polymers can be prepared by the UV-initiated click polymerizations of terminal monoynes with dithiols. 14 With applications in high performance polymer, [15][16][17] optical, 18,19 luminescent, 20 opto-electronic, 21 self-healing, 2,22 metal adsorption 23 and other fields, these polymers are in high demand.…”