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This work demonstrates the successful blocky bromination of syndiotactic polystyrene (sPS- co -sPS-Br) copolymers containing 6–30 mol% p -bromostyrene units, using a post-polymerization functionalization method conducted in the heterogeneous gel state. For comparison, a matched set of randomly brominated sPS- co -sPS-Br copolymers was prepared using homogeneous (solution-state) reaction conditions. The degree of bromination and copolymer microstructure were evaluated using 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of gel-state (Blocky) and solution-state (Random) copolymers exhibit strikingly different resonance frequencies and peak intensities above 6 mol% Br and provide direct evidence that functionalization in the gel state produces copolymers with non-random “blocky” microstructures. Quenched films of the Blocky copolymers, analyzed using ultra-small-angle X-ray scattering (USAXS) and small-angle X-ray scattering (SAXS), show micro-phase separated morphologies, which further supports that the Blocky copolymers contain distinct segments of pure sPS and segments of randomly brominated sPS unlike their completely Random analogs. Crystallization behavior of the copolymers, examined using differential scanning calorimetry (DSC), demonstrates that the Blocky copolymers are more crystallizable and crystallize faster at lower supercooling compared to their Random analogs. Computer simulations of the blocky copolymers were developed based on the semicrystalline morphology of a 10 w/v% sPS/CCl 4 gel, to rationalize the effect of heterogeneous functionalization on copolymer microstructure and crystallization behavior. The simulations were found to agree with the microstructural analysis based on the NMR results and confirm that restricting the accessibility of the brominating reagent to monomers well removed from the crystalline fraction of the gel network produces copolymers with a greater prevalence of long, uninterrupted sPS homopolymer sequences. Thus, the blocky microstructure is advantageous for preserving desired crystallizability of the resulting blocky copolymers.
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This content will become publicly available on June 1, 2026
Blocky Selective Postpolymerization C–H Functionalization of Polyolefins
C–H functionalization of commodity polyolefins affords functional materials derived from a high‐volume, low‐cost resource. However, current postpolymerization modification strategies result in randomly distributed functionalization along the length of the polymer backbone, which has a negative impact on the crystallinity of the resultant polymers, and thus the thermomechanical properties. Here, we demonstrate an amidyl radical mediated C–H functionalization of polyolefins to access blocky microstructures, which exhibit a higher crystalline fraction, larger crystallite size, and improved mechanical properties compared to their randomly functionalized analogues. Taking inspiration from the site‐selective C–H functionalization of small molecules, we leverage the steric protection provided by crystallites and target polymer functionalization to amorphous domains in a semicrystalline polyolefin gel. The beneficial outcomes of blocky functionalization are independent of the identity of the pendant functional group that is installed through functionalization. The decoupling of functional group incorporation and crystallinity highlights the promise in accessing nonrandom microstructures through selective functionalization to circumvent traditional tradeoffs in postpolymerization modification, with potential impact in advanced materials and upcycling plastic waste.
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- Award ID(s):
- 2304548
- PAR ID:
- 10604056
- Publisher / Repository:
- Wiley-VCH
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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