Improved Characterization of Polyoxazolidinones by Incorporating Solubilizing Side Chains

Carbon dioxide-based polyoxazolidinones (POxa) are an emerging subclass of non-isocyanate polyurethanes for high temperature applications. Current POxa with rigid linkers suffer from limited solubility that hinders synthesis and characterization. Herein, we report the addition of alkyl and alkoxy solubilizing groups to rigid spirocyclic POxa and their poly(hydroxy­oxazolidinone) (PHO) precursors. The modified polymers were soluble in up to six organic solvents, enabling characterization of key properties (e.g., molar mass and polymer structure) using solution-state methods. Dehydration of PHO to POxa changed solubility from highly polar to less polar solvents and improved thermal stability by 76–102 °C. The POxa had relatively high glass transition (85–119 °C) and melting (190–238 °C) temperatures tuned by solubilizing group structure. The improved understanding of factors affecting solubility, structure–property relationships, and degradation pathways gained in this study broadens the scope of soluble POxa and enables more rational design of this promising class of materials

Improved Characterization of Polyoxazolidinones by Incorporating Solubilizing Side Chains

Carbon dioxide-based polyoxazolidinones (POxa) are an emerging subclass of non-isocyanate polyurethanes for high temperature applications. Current POxa with rigid linkers suffer from limited solubility that hinders synthesis and characterization. Herein, we report the addition of alkyl and alkoxy solubilizing groups to rigid spirocyclic POxa and their poly(hydroxy­oxazolidinone) (PHO) precursors. The modified polymers were soluble in up to six organic solvents, enabling characterization of key properties (e.g., molar mass and polymer structure) using solution-state methods. Dehydration of PHO to POxa changed solubility from highly polar to less polar solvents and improved thermal stability by 76–102 °C. The POxa had relatively high glass transition (85–119 °C) and melting (190–238 °C) temperatures tuned by solubilizing group structure. The improved understanding of factors affecting solubility, structure–property relationships, and degradation pathways gained in this study broadens the scope of soluble POxa and enables more rational design of this promising class of materials

Understanding the Insertion Pathways and Chain Walking Mechanisms of α‑Diimine Nickel Catalysts for α‑Olefin Polymerization: A ¹³C NMR Spectroscopic Investigation

Nickel α-diimine catalysts have been previously shown to perform the chain straightening polymerization of α-olefins to produce materials with melting temperatures (<i>T</i>_m) similar to linear low density polyethylene (<i>T</i>_m = 100–113 °C). Branching defects due to mechanistic errors during the polymerization currently hinder access to high density polyethylene (<i>T</i>_m = 135 °C) from α-olefins. Understanding the intricacies of nickel α-diimine catalyzed α-olefin polymerization can lead to improved ligand designs that should allow production of chain-straightened polymers. We report a ¹³C NMR study of poly­(α-olefins) produced from monomers with ¹³C-labeled carbonsspecifically 1-decene with a ¹³C-label in the 2-position and 1-dodecene with a ¹³C-label in the ω-positionusing a series of α-diimine nickel catalysts. Furthermore, we developed a mathematical model capable of quantifying the resulting ¹³C NMR data into eight unique insertion pathways: 2,1- or 1,2- insertion from the primary chain end position (1°), the penultimate chain end position (2_p^°), secondary positions on the polymer backbone (2°), and previously installed methyl groups (1_m^°). With this model, we accurately determined overall regiochemistry of insertion and overall preference for primary versus secondary insertion pathways using nickel catalysts under various conditions. Beyond this, our model provides the tools necessary for determining how ligand structure and polymerization conditions affect catalyst behavior for α-olefin polymerizations

Understanding the Insertion Pathways and Chain Walking Mechanisms of α‑Diimine Nickel Catalysts for α‑Olefin Polymerization: A ¹³C NMR Spectroscopic Investigation

Nickel α-diimine catalysts have been previously shown to perform the chain straightening polymerization of α-olefins to produce materials with melting temperatures (<i>T</i>_m) similar to linear low density polyethylene (<i>T</i>_m = 100–113 °C). Branching defects due to mechanistic errors during the polymerization currently hinder access to high density polyethylene (<i>T</i>_m = 135 °C) from α-olefins. Understanding the intricacies of nickel α-diimine catalyzed α-olefin polymerization can lead to improved ligand designs that should allow production of chain-straightened polymers. We report a ¹³C NMR study of poly­(α-olefins) produced from monomers with ¹³C-labeled carbonsspecifically 1-decene with a ¹³C-label in the 2-position and 1-dodecene with a ¹³C-label in the ω-positionusing a series of α-diimine nickel catalysts. Furthermore, we developed a mathematical model capable of quantifying the resulting ¹³C NMR data into eight unique insertion pathways: 2,1- or 1,2- insertion from the primary chain end position (1°), the penultimate chain end position (2_p^°), secondary positions on the polymer backbone (2°), and previously installed methyl groups (1_m^°). With this model, we accurately determined overall regiochemistry of insertion and overall preference for primary versus secondary insertion pathways using nickel catalysts under various conditions. Beyond this, our model provides the tools necessary for determining how ligand structure and polymerization conditions affect catalyst behavior for α-olefin polymerizations