About

Craig Hawker is a professor in the Departments of Materials, Chemistry, and Biochemistry at UC Santa Barbara. His research focuses on materials science and chemistry, contributing to the understanding and development of advanced materials. As a faculty member at the Materials and Research Laboratory, he is involved in leading research initiatives and mentoring students and postdoctoral researchers in the field of materials chemistry.

Research topics

• Materials science
• Nanotechnology
• Chemistry
• Organic chemistry
• Composite material
• Polymer chemistry
• Computational chemistry
• Biochemical engineering
• Chemical engineering
• Polymer science
• Physical chemistry
• Biotechnology
• Chemical physics
• Physics

Selected publications

• From Lipoic Acid to 1,2-Dithianes: Expanding Radical Ring-Opening to Less-Activated Monomers Such as Vinyl Acetate

  Journal of the American Chemical Society · 2026-03-02

  articleSenior authorCorresponding

  Polymers containing cleavable functionality along the backbone represent a path to reduce the environmental persistence of commodity rubbers and plastics. One route to installing cleavable functionality involves the radical ring-opening polymerization of five-membered 1,2-dithiolanes such as α-lipoic acid, which introduces disulfide bonds into vinyl polymer backbones. However, the ring strain and electronics of 1,2-dithiolanes generally restrict reactivity to only favor copolymerization with more-activated comonomers, such as acrylate and styrene derivatives. Here, we show that the six-membered cyclic disulfide, 1,2-dithiane overcomes this limitation under simple thermal free-radical conditions. We demonstrate that 1,2-dithiane copolymerizes efficiently with the less-activated monomer vinyl acetate. In sharp contrast to α-lipoic acid and its derivatives, 1,2-dithiane exhibits nearly ideal copolymerization across different feed ratios, affording high conversions of both monomers (>90%), tunable molar masses (Mn ≈ 10–100 kg mol–1), and scalability (>20 g). Moreover, the 1,2-dithiane scaffold is synthetically versatile: a 1,2-dithiane-4,5-diol was synthesized from dithiothreitol as a building block for further derivatization. By varying dithiane functionality and loading, poly(dithiane-co-vinyl acetate) copolymers span semicrystalline to elastomeric mechanical properties and, critically, embed backbone-cleavable sulfur motifs (including monothioacetal units) even at low (<1 mol %) loadings. This operationally simple reaction highlights the key influence of ring size in the copolymerization behavior of disulfide-containing monomers and demonstrates the practical advantages of using 6-membered cyclic disulfides as renewable building blocks for creating degradable vinyl copolymers derived from inexpensive, industrially relevant feedstocks.

  PublisherDOI

• From Lipoic Acid to1,2-Dithianes: Expanding RadicalRing-Opening to Less-Activated Monomers Such as Vinyl Acetate

  Figshare · 2026-03-02

  articleSenior author

  Polymers containing cleavable functionality along the backbone represent a path to reduce the environmental persistence of commodity rubbers and plastics. One route to installing cleavable functionality involves the radical ring-opening polymerization of five-membered 1,2-dithiolanes such as α-lipoic acid, which introduces disulfide bonds into vinyl polymer backbones. However, the ring strain and electronics of 1,2-dithiolanes generally restrict reactivity to only favor copolymerization with more-activated comonomers, such as acrylate and styrene derivatives. Here, we show that the six-membered cyclic disulfide, 1,2-dithiane overcomes this limitation under simple thermal free-radical conditions. We demonstrate that 1,2-dithiane copolymerizes efficiently with the less-activated monomer vinyl acetate. In sharp contrast to α-lipoic acid and its derivatives, 1,2-dithiane exhibits nearly ideal copolymerization across different feed ratios, affording high conversions of both monomers (>90%), tunable molar masses (<i>M</i>_n ≈ 10–100 kg mol^–1), and scalability (>20 g). Moreover, the 1,2-dithiane scaffold is synthetically versatile: a 1,2-dithiane-4,5-diol was synthesized from dithiothreitol as a building block for further derivatization. By varying dithiane functionality and loading, <i>poly</i>(dithiane-<i>co</i>-vinyl acetate) copolymers span semicrystalline to elastomeric mechanical properties and, critically, embed backbone-cleavable sulfur motifs (including monothioacetal units) even at low (<1 mol %) loadings. This operationally simple reaction highlights the key influence of ring size in the copolymerization behavior of disulfide-containing monomers and demonstrates the practical advantages of using 6-membered cyclic disulfides as renewable building blocks for creating degradable vinyl copolymers derived from inexpensive, industrially relevant feedstocks.

  DOI

• Light-Programmable Morphology in Photothermal Polyurethanes Based on Stenhouse Salt as Photothermal Agent

  Journal of the American Chemical Society · 2026-05-15

  articleCorresponding

  Spatially controlled photothermal heating has enabled multiple advances in soft robotics, adaptive structures, and information encoding, but most implementations require multistep processing to localize photothermal additives. Here we report semicrystalline thermoplastic polyurethanes with backbone-integrated Stenhouse salt chromophores that enable single-step, micron-scale photopatterning and spatially selective photothermal heating (ΔT ≈ 15 °C) while retaining host mechanical performance (E ≈ 300 MPa; σy ≈ 12 MPa). A triflic acid-catalyzed step-growth synthesis tolerates the ionic Stenhouse salt diol, providing scalable, one-pot access to functional semicrystalline polyurethanes. White-light irradiation through a photomask is shown to trigger an irreversible cyclopentenone-forming rearrangement that permanently photobleaches exposed regions while preserving photothermal activity in masked areas. Subsequent green-light illumination heats the colored domains above the melting transition, while bleached regions remain below it, creating coexisting amorphous and semicrystalline zones within a single film. This light-addressable control over local crystallinity yields photothermal materials with spatially programmed mechanics, including sequential yielding, without additive redistribution.

  PublisherDOI

• CCDC 2503979: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2026-03-03

  datasetOpen accessSenior author

  An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  PublisherDOI

• From Lipoic Acid to1,2-Dithianes: Expanding RadicalRing-Opening to Less-Activated Monomers Such as Vinyl Acetate

  Figshare · 2026-03-02

  otherSenior author

  Polymers containing cleavable functionality along the backbone represent a path to reduce the environmental persistence of commodity rubbers and plastics. One route to installing cleavable functionality involves the radical ring-opening polymerization of five-membered 1,2-dithiolanes such as α-lipoic acid, which introduces disulfide bonds into vinyl polymer backbones. However, the ring strain and electronics of 1,2-dithiolanes generally restrict reactivity to only favor copolymerization with more-activated comonomers, such as acrylate and styrene derivatives. Here, we show that the six-membered cyclic disulfide, 1,2-dithiane overcomes this limitation under simple thermal free-radical conditions. We demonstrate that 1,2-dithiane copolymerizes efficiently with the less-activated monomer vinyl acetate. In sharp contrast to α-lipoic acid and its derivatives, 1,2-dithiane exhibits nearly ideal copolymerization across different feed ratios, affording high conversions of both monomers (>90%), tunable molar masses (<i>M</i>_n ≈ 10–100 kg mol^–1), and scalability (>20 g). Moreover, the 1,2-dithiane scaffold is synthetically versatile: a 1,2-dithiane-4,5-diol was synthesized from dithiothreitol as a building block for further derivatization. By varying dithiane functionality and loading, <i>poly</i>(dithiane-<i>co</i>-vinyl acetate) copolymers span semicrystalline to elastomeric mechanical properties and, critically, embed backbone-cleavable sulfur motifs (including monothioacetal units) even at low (<1 mol %) loadings. This operationally simple reaction highlights the key influence of ring size in the copolymerization behavior of disulfide-containing monomers and demonstrates the practical advantages of using 6-membered cyclic disulfides as renewable building blocks for creating degradable vinyl copolymers derived from inexpensive, industrially relevant feedstocks.

  DOI

• Data-Efficient Methods for Determining Flory–Huggins χ Parameters in Multicomponent Polymer Formulations

  Macromolecules · 2025-11-12 · 1 citations

  article

  Polymer formulations are essential in diverse applications including personal care products, coatings, paints, adhesives, and plastic materials. Designing these formulations requires navigating large, complex design spaces, where phase and self-assembly behavior critically impact performance. The Flory–Huggins χ parameter, which quantifies segmental miscibility, is widely used to parametrize the excess free energy of mixing in formulation models. In this work, we introduce two data-efficient, top-down methods for estimating χ parameters using the Random Phase Approximation (RPA): (i) Boundary Nonlinear Regression (Boundary-NLR), which fits theoretical spinodal boundaries to experimental phase boundaries, and (ii) Surrogate Model Inverse Parameter Estimation (SMIPE), which uses a Gaussian Process Classifier to fit sparse phase maps via a surrogate model. Both methods allow rapid parametrization of polymer field-theoretic models without the need for additional experiments. We evaluate these approaches on data sets involving polymer–solvent–nonsolvent ternary mixtures and block copolymer–solvent systems, demonstrating their robustness to experimental noise and their relevance for real-world formulation design.

  PublisherDOI

• Radical‐Free Digital Light Processing 3D Printing of Hydrogels Using a Photo‐Caged Cyclopentadiene Diels–Alder Strategy

  Advanced Functional Materials · 2025-08-15 · 2 citations

  articleOpen accessCorresponding

  Abstract Light‐controlled chemical reactions have driven major advances in photo‐patterning and 3D printing, particularly for applications requiring spatially and temporally resolved control over soft material assembly. Synthetic hydrogels, which mimic the extracellular matrix, are widely used in 3D cell culture, drug delivery, and soft device platforms. While radical‐mediated photo‐crosslinking dominates digital light processing (DLP) bioprinting, the high reactivity of free radicals can compromise cell/biomolecule stability and functional group integrity. This issue has led to a shift toward radical‐free, light‐controlled crosslinking. In this study, a novel approach is presented for the first demonstration of radical‐free aqueous photo‐resins for DLP printing, utilizing photo‐caged cyclopentadiene (Cp) moieties and maleimide click partners. Upon 365 nm light exposure, uncaged Cp reacts rapidly with maleimide groups via a Diels–Alder cycloaddition, enabling fast gelation and high‐fidelity DLP printing. The two‐component resin system offers tunable mechanical properties and yields printed features with submillimeter fidelity. Critically, the resulting materials retain unreacted functional handles, enabling spatially resolved post‐functionalization with small molecules in the complete absence of radicals. This platform not only provides a robust and orthogonal alternative to traditional photo‐resins, but also opens new avenues for biofabrication, adaptive soft materials, and 4D‐printed systems where chemical precision and compatibility are paramount.

  PublisherOA PDFDOI

• Controlled Synthesis of Lipoate Homopolymers via Reversible Addition–Fragmentation Chain Transfer Polymerization

  Journal of the American Chemical Society · 2025-10-06 · 8 citations

  articleCorresponding

  Polylipoates (PLp), derived from α-lipoic acid, are promising polymers for developing biocompatible, stimuli-responsive, and fully (closed-loop) recyclable materials. However, their synthesis is hindered by two key challenges: the high propensity of lipoate propagating radicals to undergo backbiting during polymerization, and the tendency for polymers to spontaneously depolymerize due to a low ceiling temperature. In this study, we demonstrate that reversible addition–fragmentation chain transfer (RAFT) polymerization overcomes these challenges and can be used to synthesize PLp homopolymers with a high degree of control. This was confirmed by a linear relationship between molecular weight (Mn) and monomer conversion, as well as first-order polymerization kinetics, characteristics not achievable with conventional radical polymerization. By adjusting the RAFT agent feed ratio, the Mn of homopolymer PLps was precisely controlled with an Mn ranging from 3.6 to 62.6 kg mol–1. RAFT polymerization provided stable end-groups that effectively suppressed the spontaneous depolymerization of PLp. Polymers synthesized using RAFT agents remained intact for over 2 weeks in both solution and bulk, while those prepared under traditional radical conditions showed substantial degradation. Moreover, the trithiocarbonate end-group enabled light-triggered, on-demand depolymerization back to the original monomer. RAFT was also successfully extended to the synthesis of degradable block copolymers. Together, these results demonstrate that RAFT offers a simple, accessible, and proven strategy to address key challenges in PLp synthesis and long-term stability.

  PublisherDOI

• Amphiphilic Fluorinated Block Copolymer Additives for Ultrastable Aqueous Zn-Ion Batteries

  Journal of the American Chemical Society · 2025-12-17 · 6 citations

  article

  In this study, we explored a high-throughput automated chromatography strategy for fast screening high-performance fluorinated block copolymers as electrolyte additives for ultrastable Zn-ion batteries. The proposed polymer, synthesized through controlled reversible addition–fragmentation chain-transfer (RAFT) polymerization, features a hydrophilic oligo(ethylene glycol) methyl ether acrylate (OEGA) block to provide water solubility, and a fluorophilic perfluoropolyether (PFPE) segment as the fluorine source. Our investigations reveal that the balance between OEGA and fluorine plays a key role in modulating interactions between Zn2+ and the fluorinated polymer additives. The degree of polymerization (DP) of OEGA affects both the coordination environment of Zn2+ and water and the exposure of the hydrophobic fluorinated core. Meanwhile, the fluorinated segment facilitates the formation of a protective ZnF2-rich layer, contributing to the stabilization of the solid electrolyte interphase (SEI). Benefiting from this synergistic effect, the polymer additive significantly improves battery performance, achieving stable cycling for 3800 h in symmetric Zn|Zn cells with a Coulombic efficiency (CE) of over 99.6% in Zn|Cu cells. Notably, the Zn|NVO full cell demonstrates excellent capacity retention, maintaining 98.4% of its initial capacity after 5000 cycles at 5 A g–1, with a per-cycle capacity decay as low as 0.00032%. In addition, the Zn|NVO pouch cell delivers stable cycling with a capacity retention of 92% after 700 cycles. This work highlights the important role of composition balance in developing fluorinated polymer additives, puts forward valuable molecular design guidelines for functional additives for practical energy storage applications.

  PublisherDOI

• Topology-Dependent Polymer Stretching and Scission in Solution at Extreme Shear Rates

  ACS Polymers Au · 2025-11-18 · 1 citations

  articleOpen access

  There has been significant interest in the engineering of polymer topology to control rheology and mechanical stability in dilute solutions for applications involving extreme shear rate flows. However, methods to experimentally probe properties at relevant shear rates (≈ 104–106 s–1) have remained ex situ, obscuring access to measures of polymer deformation and rheology that would otherwise provide mechanistic insight into the topology-dependent properties that control their behavior in extreme shear flows. In this study, we used novel in situ small angle neutron scattering measurements in a capillary rheometer (capillary rheo-SANS) to simultaneously measure solution viscosities and polymer deformations in high shear on a series of chemically homologous topology-defined polymers including linear, randomly branched, and star-shaped molecules. We demonstrate that differences in the onset of chain stretching and shear thinning of these polymers in dilute solution are controlled primarily by differences in their molecular relaxation time. These differences correlate with differences in chain scission inferred from ex situ measurements at more extreme shear rates. Together, the results demonstrate a direct coupling between chain deformation and scission, and suggest that the dominant effect of branching as a means to impart resilience against mechanical degradation is through differences in relaxation dynamics due to branching. We anticipate that these results will provide key insights to engineer topology-controlled polymers for rheological modification, mechanical stability, and controlled mechano-chemistry.

  PublisherDOI

Recent grants

• Center of Excellence for Materials Research and Innovation at UCSB

  NSF · $19.1M · 2011–2018

• Robust, Efficient and Orthogonal Synthesis of Polymeric Materials

  NSF · $453k · 2010–2014

• MRSEC: Materials Research Science and Engineering Center at UCSB

  NSF · $21.2M · 2005–2012

• Highly Efficient and Versatile Synthesis of Polymeric Materials using Click Chemistry

  NSF · $420k · 2005–2009

Frequent coauthors

• Thomas P. Russell

  Lawrence Berkeley National Laboratory

  181 shared

• Edward J. Krämer

  138 shared

• Éric Drockenmuller

  Ingenierie des Materiaux polymeres

  136 shared

• Jean M. J. Fréchet

  109 shared

• Joona Bang

  Korea University

  108 shared

• Javier Read de Alaniz

  University of California, Santa Barbara

  107 shared

• Michael L. Chabinyc

  University of California, Santa Barbara

  104 shared

• Nathaniel A. Lynd

  The University of Texas at Austin

  77 shared

Labs

• Craig Hawker GroupPI

  Meet the members of the Hawker Group.