Arm‐first synthesis of star polymers with polywedge arms using ring‐opening metathesis polymerization and bifunctional crosslinkers

Abstract

This work presents a two-step, one-pot process to make star polymers with polywedge arms. In a one-pot reaction, after the polywedge arms are synthesized, crosslinker species are added to the reaction, rapidly forming star polymers. Crosslinker species with different degrees of conformational freedom were designed and synthesized and their capacity to generate star polymers was evaluated. Mass conversions up to 92% and stars with up to 17 arms were synthesized with the most rigid crosslinker. The effects of arm molecular weight and molar ratio of crosslinker to arm on mass conversion and arms per star were explored further. Finally, the size-molecular weight scaling relationship for polywedges with linear and star architectures was compared, corroborating theoretical results regarding star polymers with arms much larger than their core.

Rapid and Efficient Synthesis of Star Polymers via Arm-First Monomer Emulsified Aqueous Ring-Opening Metathesis Polymerization (ME-ROMP)

“…Miyake and co-workers have addressed this challenge by employing a dinorbornene (di-NB) cross-linker with a rigid conformation that facilitates the reduction of intramolecular cross-linking, thereby enabling the synthesis of star polymers with relatively high arm conversion and molecular weight. 46 Similar result reported by Xia and coworkers by using a rigid ladder-like di-NB cross-linker, prepared star polymers with high arm conversion and molar mass up to 430 kDa. 47 Another way to enhance the intermolecular crosslinking is to increase the feed ratio of the cross-linker, under the premise that no macrogel is formed.…”

“…However, a significant challenge associated with the arm-first ROMP approach lies in the inevitable occurrence of intramolecular cross-linking (metathesis reaction of cross-linkers at the one chain end) that greatly restricts the formation of high-molecular-weight star polymers with complete arm conversion. Miyake and co-workers have addressed this challenge by employing a dinorbornene (di-NB) cross-linker with a rigid conformation that facilitates the reduction of intramolecular cross-linking, thereby enabling the synthesis of star polymers with relatively high arm conversion and molecular weight . Similar result reported by Xia and co-workers by using a rigid ladder-like di-NB cross-linker, prepared star polymers with high arm conversion and molar mass up to 430 kDa .…”

“…In addition to demonstrating the advancement of arm-first ME-ROMP, a control experiment of synthesizing star-poly­( M1 ) 25 via the typical homogeneous ROMP in pure CH 2 Cl 2 with the feeding ratio of [ M1 ]:[G3]:[ C1 ] = 25:1:5 was performed for more than 6 h. It should be noted that the CH 2 Cl 2 ROMP was conducted in a nitrogen-filled glovebox, due to the requirement of long reaction time for core formation as reported elsewhere. , As indicated by the SEC results (Figure d), the ROMP in CH 2 Cl 2 produced star-poly­( M1 ) 25 with only 64% of arm conversions and M w,MALLS = 57 kDa (Table ). Compared with the homogeneous ROMP in CH 2 Cl 2 , the ME-ROMP with the same feeding ratio produced star-poly­( M1 ) 25 with a much higher arm conversion and molecular weight (Conv.…”

Multiarm Core Cross-Linked Star-Shaped Poly(2-oxazoline)s Using a Bisfunctional 2-Oxazoline Monomer

“…This method is the least suitable for industrial applications as multiple purification steps and long reaction times are often required . The arm-first (or CCS) method allows for the synthesis of stars with well-defined arms that can reach into the hundreds and large cores. − The potential to form large, hydrophobic cores makes them highly suited for drug encapsulation applications. Nevertheless, core cross-linked stars have the disadvantage of being less well defined and thus more challenging to analyze.…”

Progress of Application of Ring-Opening Metathesis Polymerization (ROMP) in the Synthesis of Star Polymers

“…Miyake 等 [25] 研究了交联剂的柔性对星型聚合物合 成效率的影响, 如图 1c, R 基团为不同链长的不同刚柔 性连接基团. 结果发现交联剂的刚性越强, 聚合物臂的 转化率越高, 所得星型聚合物的分子量越高.…”