Dynamic Crosslinking Research Articles

Preparation of bio-based and phosphorus-free functional coatings for flame retardant, UV-resistance and antibacterial silk fabric

To endow silk with multifunctionality and expand its application fields, the silk fabric was treated with protocatechualdehyde to prepare a novel silk fabric with Schiff base structure (CAT@Silk). Then, CAT@Silk was immersed in iron (III) solution to chelate Fe3+ to obtain flame retardant, antibacterial and UV-resistant silk fabric (CAT@Fe@Silk). Compared with the limiting oxygen index (LOI) value of the original silk, the CAT@Fe@Silk increased from 23.3 % to 35.1 %, and remained 32.4 % even after 20 laundering cycles (LCs), indicating excellent flame retardant durability. The UV protection coefficient of CAT@Fe@Silk was 67.74, which was higher than that of the original sample (21.02). In addition, CAT@Fe@Silk had good antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This work constructed a dynamic cross-linking network that mimicked the adhesion of mussels generating from the complexation of catechol groups and Fe3+ ions (catechol-Fe3+), which not only endowed silk fabric with good flame retardancy, but also with UV resistance and antibacterial properties, demonstrating good potential application.

Self-healing, adaptive and shape memory polymer-based thermal interface phase change materials via boron ester cross-linking

Addressing the thermal resistance between rough interfaces without applying pressure to the interfacial sandwich has been a challenge. Herein, a thermal interface phase change material (TIPCM) is designed to realize a 3D support skeleton with a dynamic crosslinking network by introducing a boron ester crosslinking backbone into paraffin wax (PW) and ethylene-octene copolymer (EOC), thus enabling the TIPCM to ensure mechanical integrity without leakage even above the melting temperature of EOC. The chemical cross-linking between the organic solid–liquid phase change material (PCM) and the polymer realizes thermally triggered self-healing and adaptive shape memory properties. The phase transition of PW leads to a decrease in the modulus of TIPCM and activates the ester exchange of the dynamic covalent bonding of boron esters, which allows TIPCM to self-heal and self-adapt to a variety of object surfaces. These enabled the TIPCM to fill the interface gaps through small stress deformations, forming an interlocking structure that reduces contact thermal resistance and promotes heat transfer. The obtained TIPCM achieves excellent chip thermal management performance, cooling the analog CPU temperature by 67 °C at 5 V. In conclusion, this study provides a potential strategy for redesigning TIPCMs with high latent heat and special physical properties for thermal management.

Flexible and recyclable thermally conductive phase change composites with shape stability

AbstractForm‐stable and flexible highly thermally conductive phase change composites are crucial for thermal management. In this work, based on the associative exchangeable crosslinkers derived from the reaction of epoxidized soybean oil (ESO) and sebacic acid (SA), a kind of flexible and recyclable thermally conductive phase change composite with shape stability is prepared. The shape stabilization is achieved through the co‐cooperation of expanded graphite (EG) and the dynamic covalent crosslinking network. The thermal conductivity is enhanced by embedding with boron nitride (BN). When the mass fraction of BN is 25%, the thermal conductivity of the composite can reach 4.03 W/(m·K). The results indicate that the prepared PCMs composites have excellent flexibility and form stability, suggesting the potential application in the thermal management for electronic devices. The presence of dynamic exchangeable bonds makes the matrix degradable under mild conditions, enabling the recycling of valuable thermally conductive fillers, which proves to be highly sustainable. This work introduces a novel method for preparing flexible and recyclable thermally conductive phase change composites with shape stability vitrimer.

Synthesis of Photoresponsive Fast Self-healing Polyolefin Composites by Nickel-Catalyzed Copolymerization of Ethylene and Lignin Cluster Monomers.

Polymers may suffer from sudden mechanical damages during long-term use under various harsh operating environments. Rapid and real-time self-healing will extend their service life, which is particularly attractive in the context of circular economy. In this work, a lignin cluster polymerization strategy (LCPS) was designed to prepare a series of lignin functionalized polyolefin composites with excellent mechanical properties through nickel catalyzed copolymerization of ethylene and lignin cluster monomers. These composites can achieve rapid self-healing within 30 seconds under a variety of extreme usage environments (underwater, seawater, extremely low temperatures as low as -60 °C, organic solvents, acid/alkali solvents, etc.), which is of great significance for real-time self-healing of sudden mechanical damage. More importantly, the dynamic cross-linking network within these composites enable great re-processability and amazing sealing performances.

Effect of active carbonyl-carboxyl ratio on dynamic Schiff base crosslinking and its modulation of high-performance oxidized starch-chitosan hydrogel by hot extrusion 3D printing

The quest to develop 3D starch-based printing hydrogels for the controlled release of active substances with excellent mechanical and printing properties has gained significant attention. This work introduced a facile method based on crosslinking via Schiff base reaction for preparing bicomponent hydrogels. The method involved the utilization of customizable oxidized starch (OS) and chitosan (CS), enabling superior printing performance through the precise control of various active carbonyl-carboxyl ratios (ACR, 2:1, 1:1, and 2:3, respectively) of OS. OS-CS hydrogel (OSC) with an ACR level of 2:1 (OS-2-y%CS) underwent rearrangement during printing environment, fostering increased Schiff base reaction with a higher crosslinking degree and robust high structural recovery (>95 %). However, with decreasing ACR levels (from 2:1 to 2:3), the printing performance and mechanical strength of printed OSC (POSC) declined due to lower Schiff base bonds and increased phase separation. Compared with printed OS, POS-2-2%CS exhibited a remarkable 1250.52 % increase in tensile strength and a substantial 2424.71 % boost in compressive strength, enhanced shape fidelity and notable self-healing properties. Moreover, POS-2-2%CS exhibited stable diffusive drug release, showing potential application in the pH-responsive release of active substances. Overall, controlling the active carbonyl-carboxyl ratios provided an efficient and manageable approach for preparing high-performance 3D-printed hydrogels.

Tunicate cellulose nanocrystals strengthened injectable stretchable hydrogel as multi-responsive enhanced antibacterial wound dressing for promoting diabetic wound healing

The intricate microenvironment of diabetic wounds characterized by hyperglycemia, intense oxidative stress, persistent bacterial infection and complex pH fluctuations hinders the healing process. Herein, an injectable multifunctional hydrogel (QPTx) was developed, which exhibited excellent mechanical performance and triple responsiveness to pH, temperature, and glucose due to dynamic covalent cross-linking involving dynamic Schiff base bonds and phenylboronate esters with phenylboronic-modified quaternized chitosan (QCS-PBA), polydopamine coated tunicate cellulose crystals (PDAn@TCNCs) and polyvinyl alcohol (PVA). Furthermore, the hydrogels can incorporate insulin (INS) drugs to adapt to the complex and variable wound environment in diabetic patients for on-demand drug release that promote diabetic wound healing. Based on various excellent properties of the colloidal materials, the hydrogels were evaluated for self-healing, rheological and mechanical properties, in vitro insulin response to pH/temperature/glucose release, antibacterial, antioxidant, tissue adhesion, coagulation, hemostasis in vivo and in vitro, and biocompatibility and biodegradability. By introducing PDAn@TCNCs particles, the hydrogel has photothermal antibacterial activity, enhanced adhesion and oxidation resistance. We further demonstrated that these hydrogel dressings significantly improved the healing process compared to commercial dressings (Tegaderm™) in full-layer skin defect models. All indicated that the glucose-responsive QPTx hydrogel platform has great potential for treating diabetic wounds.

Six-membered ring-reinforced flexible high-elongation block polyamide as strong and multi-reusable hot melt adhesive

This study presented the synthesis and characterization of polyester block polyamide hot melt adhesives (PPHMAs) with high adhesion strength and toughness. The PPHMAs demonstrated an adhesion strength of 11.04 MPa and toughness of 22.54 MJ·m−3, making them suitable for various substrates such as aluminum, copper, and stainless steel. The polyamide segments synthesized from dimer acid and 2-methyl-1,5-diaminopentane exhibited characteristics of softness and high elongation. Using isophorone diamine as a reinforcing agent introduced a stable six-membered ring structure, which enhanced the polymer's rigidity and strength, thus meeting the requirements for polyamide segments to function as the hard segments in block polymers. A trace amount of Tris (2-aminoethyl) amine provided the cross-linking sites which are similar to those in neuronal structures. The polyester segments, which were synthesized from poly (propylene glycol) diglycidyl ether and sebacic acid, served as the soft segments in the block polymer and were connected to the hard segment via amide bonds. The addition of the polyester segments enhanced the non-covalent molecular interactions within PPHMAs, leading to dynamic crosslinking properties. The adhesive maintained stable adhesion even after six cycles, which showcased its durability. Furthermore, the PPHMAs exhibited notable chemical resistance. It retained over 60 % adhesion strength after exposure to some chemical solvents including artificial seawater, 5 % NaOH solution, 5 % HCl solution, and DMSO for 24 h. These findings offered a novel approach to enhancing the adhesion strength and toughness of conventional thermoplastic hot melt adhesives.

Poly(ethylene glycol)-based polyurethanes based on dynamic oxime-urethane bonds for sustainable thermal energy storage

Traditional poly(ethylene glycol)-based polyurethane phase change materials (PUPCMs) are difficult to reprocess and non-recyclable because of their permanently cross-linking structure, leading to issues of resource waste. To overcome this problem, this study introduces dynamic bonds in PUPCMs to develop dynamic cross-linking networks. A series of polyurethane phase change materials containing dynamic oxime-urethane bonds (DOU-PUPCMs) are prepared using poly(ethylene glycol) (PEG), dimethylglyoxime (DMG) and hexamethylene diisocyanate (HDI) as raw materials. It has been shown that the obtained DOU-PUPCMs exhibit good heat storage capability and outstanding thermal stability. Importantly, the introduction of oxime-urethane groups provided DOU-PUPCMs with processibility. After multiple reprocessing cycles, the chemical structure and energy storage capacity of the DOU-PUPCMs essentially remain consistent with the original samples. The breaking and restructuring of oxime-urethane bonds and hydrogen bonds in DOU-PUPCMs makes them recyclable. This is not only significant for the development of recyclable and sustainable energy storage materials, but also complements studies such as the application of oxime-urethane bonds to PCMs.

Efficient and Robust Dynamic Crosslinking for Compatibilizing Immiscible Mixed Plastics through In Situ Generated Singlet Nitrenes.

Creating a sustainable economy for plastics demands the exploration of new strategies for efficient management of mixed plastic waste. The inherent incompatibility of different plastics poses a major challenge in plastic mechanical recycling, resulting in phase-separated materials with inferior mechanical properties. Here, this study presents a robust and efficient dynamic crosslinking chemistry that effectively compatibilizes mixed plastics. Composed of aromatic sulfonyl azides, the dynamic crosslinker shows high thermal stability and generates singlet nitrene species in situ during solvent-free melt-extrusion, effectively promoting C─H insertion across diverse plastics. This new method demonstrates successful compatibilization of binary polymer blends and model mixed plastics, enhancing mechanical performance and improving phase morphology. It holds promise for managing mixed plastic waste, supporting a more sustainable lifecycle for plastics.

SYNTHESIS AND STUDY OF THE INFLUENCE OF ALKALI CONCENTRATION AND TEMPERATURE ON THE PHYSICOCHEMICAL PROPERTIES OF CRYOGELS BASED ON GELATIN AND CHITOSAN

Much of the polymer research is focused on improving existing polymers or developing new biomaterials with tunable properties. Natural polymers that have certain segments that contribute to an additional therapeutic effect are more often used as a biocompatible polymer. Polymers can be produced using a variety of methods, including covalent cross-linking, dynamic covalent cross-linking, physical cross-linking, cryopolymerization, 3D printing, electrospinning, etc. Cryopolymerization is a unique method and has several advantages over other methods. By cryofreezing it is possible to obtain a porous structure in which the size and volume of the pores can be controlled by changing the concentration of the initial monomers and temperature. The purpose of this study is to determine the effect of alkali concentration and cryopolymerization temperature on the properties of cryogels. The objects of study in this work are cryogels based on gelatin and chitosan. Methodology. The functional groups of the cryogels were determined by IR spectroscopy. The results of a study of the sorption and desorption of polymers are presented. The results of polymer degradation in phosphate-saline solution over 8 weeks are also shown. These studies were based on changes in mass, that is, they were carried out using the gravimetric method. Conclusion. The results of a study of the influence of alkali concentration and temperature on the physicochemical properties of cryogels based on gelatin and chitosan are presented. Cryogels based on gelatin and chitosan are synthesized without the use of harmful chemical cross-linking agents, which makes them attractive for tissue engineering.

Rosin-based self-healing functionalized composites with two-dimensional polyamide for antimicrobial and anticorrosion coatings

The design of polymer-based composites possessing good mechanical and self-healing properties remains a challenge in the development of high-performance self-healing materials. In this study, we used two-dimensional polyamide (2DPA), biomass rosin ester, and a dynamic crosslinking agent poly (urethane-urea) as raw materials, and prepared biomass rosin-based composites via in situ polymerization. The composites with 1 wt% 2DPA exhibited excellent self-healing properties (self-healing efficiency of 94 % after 24 h at 80 °C) and mechanical properties (tensile strength = 7.8 MPa). Moreover, the composites were applied to anticorrosion and antimicrobial coatings, which possessed excellent anticorrosion and antimicrobial properties. This study provides a new strategy for developing high-performance bio-based self-healing composites.

Stable operation of SiO anodes enabled by a multifunctional molecular crosslinker

SiO anodes are promising for energy-dense lithium-ion batteries, however, they suffer from short cycle life caused by large volume change (∼200%) and low initial Coulomb efficiency (ICE). Herein, we report a conceptual strategy to boost the electrochemical performance of SiO by enhancing the interaction between binders and conductive additives via a molecular crosslinker with both pyrene ring and adamantyl group (AdPy). Benefiting from the inclusion interaction between beta-cyclodextrin polymers (βCDp) and AdPy as well as the π-π interaction between single-walled carbon nanotube (SWCNT) and AdPy, a robustly conductive and adhesive network is constructed for maintaining integral electrode structure and robust conductive network during charge/discharge cycles. The resultant SiO electrode with SWCNT/AdPy-βCDp networks achieves larger initial capacity, higher ICE and better cycle stability than those of SiO electrode with SWCNT/βCDp complex, indicating the key role of AdPy crosslinker in enhancing electrochemical performance. Experimental results suggest that the interaction between binders and conductive additives can effectively alleviate stress generated from SiO volume changes during cycling. This work provides a promising platform to construct dynamic cross-linking conductive and adhesive network for boosting the lithium storage performance of high-capacity electrode materials.

Designing Conductive Pyrrolidinium‐Based Dual Network Gel Electrolytes: Tailoring Performance with Dynamic and Covalent Crosslinking

AbstractTransitioning toward a carbon‐negative direction necessitates continued development and enhancement of existing lithium battery technologies. A key impediment for these technologies is the utilization of flammable organic solvent‐based electrolytes, which pose significant safety risks. Furthermore, the recyclability of batteries has not reached the level required for transitioning to a circular economy. Here, poly(ionic liquid)‐based dual network gel electrolytes are reported as safer and sustainable alternative materials. The materials employ both, dynamic (up to 45 mol%) and covalent crosslinking (up to 10 mol%), allowing the fabrication of mechanically stable gels with a high content (up to 65 wt%) of ionic liquid/salt both via thermal and photo polymerization. The dual nature of this network in interplay with other key components is systematically investigated. Mechanical stability (up to 0.7 MPa), combined with enhanced ionic conductivity (surpassing 10−4 S cm−1 at room temperature) is achieved via the synergetic combination of dynamic non‐covalent and covalent crosslinking, resulting in improved electrochemical (up to 5 V) and thermal stability (reaching 300 °C) by the embedded ionic liquid. Moreover the presence of the dynamic crosslinks facilitates reprocessing at 70 °C without comrpomising the electrochemical performance, thus reaching full recyclability and reusability.

Synthesis of polyethylene-based covalent adaptable networks including 1,2,3-triazolium or imine dynamic cross-links by reactive processing

Polyethylene-based covalent adaptable networks (PE CANs) are obtained by reactive extrusion in a micro-compounder of a commercial maleic anhydride-grafted polyethylene (PE-g-MA) with two tailor-made α,ω-diamine cross-linkers carrying either imine or 1,2,3-triazolium groups as dissociative covalent dynamic bonds. Depending on the chemical nature of the exchangeable bonds, drastically different properties are demonstrated by FTIR, swelling/extractible, reactive dissolution and rheological experiments. The imine-containing PE CAN yields a high gel fraction but rheology and reactive dissolution experiments demonstrate the lack of dynamicity due to side-reactions promoting the formation of non-dynamic covalent cross-links. Such undesirable reaction occurs already during the processing stage from the premature cleavage of the imine bonds into amines, and further formation of permanent imide cross-links by reaction with pendent maleic anhydrides. Conversely, the 1,2,3-triazolium-containing PE CAN presents a lower gel fraction but exhibits viscoelastic properties typical of dissociative CANs. While this material is easily reprocessable by compression moulding, the evolution of the rheological properties at high temperatures (160–200 °C) points toward the occurrence of side reactions slowing down the relaxation dynamics which we attribute to the chemical rearrangement of the 1,2,3-triazolium cross-links. These two examples illustrate the difficulty of using amine-functionalized dynamic cross-links in the synthesis of PE CANs by reactive extrusion using PE-g-MA.

Biomimetic Non-ergodic Aging by Dynamic-to-covalent Transitions in Physical Hydrogels.

Hydrogels are soft materials engineered to suit a multitude of applications that exploit their tunable mechanochemical properties. Dynamic hydrogels employing noncovalent, physically cross-linked networks dominated by either enthalpic or entropic interactions enable unique rheological and stimuli-responsive characteristics. In contrast to enthalpy-driven interactions that soften with increasing temperature, entropic interactions result in largely temperature-independent mechanical properties. By engineering interfacial polymer-particle interactions, we can induce a dynamic-to-covalent transition in entropic hydrogels that leads to biomimetic non-ergodic aging in the microstructure without altering the network mesh size. This transition is tuned by varying temperature and formulation conditions such as pH, which allows for multivalent tunability in properties. These hydrogels can thus be designed to exhibit either temperature-independent metastable dynamic cross-linking or time-dependent stiffening based on formulation and storage conditions, all while maintaining structural features critical for controlling mass transport, akin to many biological tissues. Such robust materials with versatile and adaptable properties can be utilized in applications such as wildfire suppression, surgical adhesives, and depot-forming injectable drug delivery systems.

Closed-loop recycling of tough epoxy supramolecular thermosets constructed with hyperbranched topological structure

The regulation of topological structure of covalent adaptable networks (CANs) remains a challenge for epoxy CANs. Here, we report a strategy to develop strong and tough epoxy supramolecular thermosets with rapid reprocessability and room-temperature closed-loop recyclability. These thermosets were constructed from vanillin-based hyperbranched epoxy resin (VanEHBP) through the introduction of intermolecular hydrogen bonds and dual dynamic covalent bonds, as well as the formation of intramolecular and intermolecular cavities. The supramolecular structures confer remarkable energy dissipation capability of thermosets, leading to high toughness and strength. Due to the dynamic imine exchange and reversible noncovalent crosslinks, the thermosets can be rapidly and effectively reprocessed at 120 °C within 30 s. Importantly, the thermosets can be efficiently depolymerized at room temperature, and the recovered materials retain the structural integrity and mechanical properties of the original samples. This strategy may be employed to design tough, closed-loop recyclable epoxy thermosets for practical applications.

Dynamic Covalent Chemistry of Enamine-Ones: Exploring Tunable Reactivity in Vitrimeric Polymers and Covalent Organic Frameworks.

Dynamic covalent chemistry (DCC) has revolutionized the field of polymer science by offering new opportunities for the synthesis, processability, and recyclability of polymers as well as in the development of new materials with interesting properties such as vitrimers and covalent organic frameworks (COFs). Many DCC linkages have been explored for this purpose, but recently, enamine-ones have proven to be promising dynamic linkages because of their facile reversible transamination reactions under thermodynamic control. Their high stability, stimuli-responsive properties, and tunable kinetics make them promising dynamic cross-linkers in network polymers. Given the rapid developments in the field in recent years, this review provides a critical and up-to-date overview of recent developments in enamine-one chemistry, including factors that control their dynamics. The focus of the review will be on the utility of enamine-ones in designing a variety of processable and self-healable polymers with important applications in vitrimers and recyclable closed-loop polymers. The use of enamine-one linkages in crystalline polymers, known as COFs and their applications are also summarized. Finally, we provide an outlook for future developments in this field.

Hyperbranched Vitrimer for Ultrahigh Energy Dissipation.

Polymers are ideally utilized as damping materials due to the high internal friction of molecular chains, enabling effective suppression of vibrations and noises in various fields. Current strategies rely on broadening the glass transition region or introducing additional relaxation components to enhance the energy dissipation capacity of polymeric damping materials. However, it remains a significant challenge to achieve high damping efficiency through structural control while maintaining dynamic characteristics. In this work, we propose a new strategy to develop hyperbranched vitrimers (HBVs) containing dense pendant chains and loose dynamic crosslinked networks. A novel yet weak dynamic transesterification between the carboxyl and boronic acid ester was confirmed and used to prepare HBVs based on poly (hexyl methacrylate-2-(4-ethenylphenyl)-5,5-dimethyl-1,3,2-dioxaborinane) P(HMA-co-ViCL) copolymers. The -type of macromonomers, the crosslinking points formed by the dynamic covalent connection via the associative exchange, and the weak yet dynamic exchange reaction are the three keys to developing high-performance HBV damping materials. We found that P(HMA-co-ViCL) 20k-40-60 HBV exhibited ultrahigh energy-dissipation performance over a broad frequency and temperature range, attributed to the synergistic effect of dense pendant chains and weak dynamic covalent crosslinks. This unique design concept will provide a general approach to developing advanced damping materials.

Hyperbranched Vitrimer for Ultrahigh Energy Dissipation

AbstractPolymers are ideally utilized as damping materials due to the high internal friction of molecular chains, enabling effective suppression of vibrations and noises in various fields. Current strategies rely on broadening the glass transition region or introducing additional relaxation components to enhance the energy dissipation capacity of polymeric damping materials. However, it remains a significant challenge to achieve high damping efficiency through structural control while maintaining dynamic characteristics. In this work, we propose a new strategy to develop hyperbranched vitrimers (HBVs) containing dense pendant chains and loose dynamic crosslinked networks. A novel yet weak dynamic transesterification between the carboxyl and boronic acid ester was confirmed and used to prepare HBVs based on poly (hexyl methacrylate‐2‐(4‐ethenylphenyl)‐5,5‐dimethyl‐1,3,2‐dioxaborinane) P(HMA‐co‐ViCL) copolymers. The ‐type of macromonomers, the crosslinking points formed by the dynamic covalent connection via the associative exchange, and the weak yet dynamic exchange reaction are the three keys to developing high‐performance HBV damping materials. We found that P(HMA‐co‐ViCL) 20k‐40‐60 HBV exhibited ultrahigh energy‐dissipation performance over a broad frequency and temperature range, attributed to the synergistic effect of dense pendant chains and weak dynamic covalent crosslinks. This unique design concept will provide a general approach to developing advanced damping materials.

A New Class of Polyion Complex Vesicles (PIC-somes) to Improve Antimicrobial Activity of Tobramycin in Pseudomonas Aeruginosa Biofilms.

Pseudomonas aeruginosa (PA) is a major healthcare concern due to its tolerance to antibiotics when enclosed in biofilms. Tobramycin (Tob), an effective cationic aminoglycoside antibiotic against planktonic PA, loses potency within PA biofilms due to hindered diffusion caused by interactions with anionic biofilm components. Loading Tob into nano-carriers can enhance its biofilm efficacy by shielding its charge. Polyion complex vesicles (PIC-somes) are promising nano-carriers for charged drugs, allowing higher drug loadings than liposomes and polymersomes. In this study, a new class of nano-sized PIC-somes, formed by Tob-diblock copolymer complexation is presented. This approach replaces conventional linear PEG with brush-like poly[ethylene glycol (methyl ether methacrylate)] (PEGMA) in the shell-forming block, distinguishing it from past methods. Tob paired with a block copolymer containing hydrophilic PEGMA induces micelle formation (PIC-micelles), while incorporating hydrophobic pyridyldisulfide ethyl methacrylate (PDSMA) monomer into PEGMA chains reduces shell hydrophilicity, leads to the formation of vesicles (PIC-somes). PDSMA unit incorporation enables unprecedented dynamic disulfide bond-based shell cross-linking, significantly enhancing stability under saline conditions. Neither PIC-somes nor PIC-micelles show any relevant cytotoxicity on A549, Calu-3, and dTHP-1 cells. Tob's antimicrobial efficacy against planktonic PA remains unaffected after encapsulation into PIC-somes and PIC-micelles, but its potency within PA biofilms significantly increases.