Self-assembly Of Polymers Research Articles

A Review of Polymeric Micelles and Their Applications.

Self-assembly of amphiphilic polymers with hydrophilic and hydrophobic units results in micelles (polymeric nanoparticles), where polymer concentrations are above critical micelle concentrations (CMCs). Recently, micelles with metal nanoparticles (MNPs) have been utilized in many bio-applications because of their excellent biocompatibility, pharmacokinetics, adhesion to biosurfaces, targetability, and longevity. The size of the micelles is in the range of 10 to 100 nm, and different shapes of micelles have been developed for applications. Micelles have been focused recently on bio-applications because of their unique properties, size, shape, and biocompatibility, which enhance drug loading and target release in a controlled manner. This review focused on how CMC has been calculated using various techniques. Further, micelle importance is explained briefly, different types and shapes of micelles are discussed, and further extensions for the application of micelles are addressed. In the summary and outlook, points that need focus in future research on micelles are discussed. This will help researchers in the development of micelles for different applications.

Conductive Collagen-Based Hydrogel Combined With Electrical Stimulation to Promote Neural Stem Cell Proliferation and Differentiation.

Injectable biomimetic hydrogels are a promising strategy for enhancing tissue repair after spinal cord injury (SCI) by restoring electrical signals and increasing stem cell differentiation. However, fabricating hydrogels that simultaneously exhibit high electrical conductivities, excellent mechanical properties, and biocompatibility remains a great challenge. In the present study, a collagen-based self-assembling cross-linking polymer network (SCPN) hydrogel containing poly-pyrrole (PPy), which imparted electroconductive properties, is developed for potential application in SCI repair. The prepared collagen/polypyrrole (Col/PPy)-based hydrogel exhibited a continuous and porous structure with pore sizes ranging from 50 to 200 μm. Mechanical test results indicated that the Young’s moduli of the prepared hydrogels were remarkably enhanced with PPy content in the range 0–40 mM. The conductivity of Col/PPy40 hydrogel was 0.176 ± 0.07 S/cm, which was beneficial for mediating electrical signals between tissues and accelerating the rate of nerve repair. The investigations of swelling and degradation of the hydrogels indicated that PPy chains interpenetrated and entangled with the collagen, thereby tightening the network structure of the hydrogel and improving its stability. The cell count kit-8 (CCK-8) assay and live/dead staining assay demonstrated that Col/PPy40 coupled with electrical simulation promoted the proliferation and survival of neural stem cells (NSCs). Compared with the other groups, the immunocytochemical analysis, qPCR, and Western blot studies suggested that Col/PPy40 coupled with ES maximally induced the differentiation of NSCs into neurons and inhibited the differentiation of NSCs into astrocytes. The results also indicated that the neurons in ES-treated Col/PPy40 hydrogel have longer neurites (170.8 ± 37.2 μm) and greater numbers of branch points (4.7 ± 1.2). Therefore, the prepared hydrogel system coupled with ES has potential prospects in the field of SCI treatment.

Abstract 299: Self-assembling nanoparticles: A novel approach for targeted cancer treatment using tumor treating fields

Abstract Tumor Treating Fields (TTFields) are used in cancer treatment as they offer increased efficacy, safety, and low adverse effects. They have shown significant potential in pancreatic cancer (PC) clinical trials when combined with chemotherapy. It is pertinent to know that although TTFields-chemotherapy combination definitely enhances the treatment efficacy, it also results in chemotherapy induced severe adverse effects. To resolve this, we earlier reported development of Gemcitabine loaded self-assembling cationic-anionic polymer nanoparticles (S-CAP NPs) capable of achieving TTFields-triggered targeted drug release at the PC tumor site. Initially, four S-CAP NPs [C4 and C7 from chitosan- bovine serum albumin (Chitosan-BSA) S-CAP NPs; P5 and P8 from polyethylenimine- bovine serum albumin (PEI-BSA) S-CAP NPs] were shortlisted [Table 1 - particle size: ~ 200 nm; % encapsulation efficiency (EE): 55-65%]. For proof-of-concept studies, effect of TTFields on the % EE and % cumulative drug release of the S-CAP-NPs was investigated. The studies revealed (Table 1) significant reduction (p value < 0.05) in the % EE of S-CAP NPs within 48h TTFields treatment, confirming that the TTFields destabilize the NPs triggering targeted drug release. Similarly, In vitro drug release studies showed significant increase (p< 0.01) in rate of drug release from S-Cap NPs in presence of TTFields. The cell inhibition assay confirmed the synergism in cell apoptosis wherein PEI-BSA S-CAP NPs showed higher efficacy compared to chitosan-BSA S-CAP NPs. Further, additional stability studies continued over a period of 18 months confirmed stable formulations. In vivo acute and chronic toxicity studies are underway to identify the most optimum dose of S-CAP NPs for further in vivo efficacy studies. To summarize, S-CAP-NPs present a promising avenue to achieve targeted chemotherapy in conjunction with TTFields. This work is supported by AACR-Novocure tumor treating fields research fellowship. Table 1. Effect of TTFields on % encapsulation efficiency (n=3). Data represented as Mean ± SD. Batch Particle size (nm) Encapsulation efficiency (%) - 0h Encapsulation efficiency (%) - 24h - 150 KHZ Encapsulation efficiency (%) - 48h - 150 KHZ Chitosan-BSA S-CAP NPs C4 210.54 ± 38.96 61.26 ± 5.11 36.21 ± 3.53 24.86 ± 3.19 C7 215.67 ± 32.55 65.31 ± 5.84 32.19 ± 2.68 21.86 ± 4.64 PEI-BSA S-CAP NPs P5 198.29 ± 41.05 58.83 ± 3.33 27.66 ± 3.31 18.96 ± 3.96 P8 209.92 ± 31.33 64.31 ± 5.13 24.83 ± 4.29 19.42 ± 2.73 Citation Format: Preshita Prafulla Desai, Sunil Prabhu. Self-assembling nanoparticles: A novel approach for targeted cancer treatment using tumor treating fields [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 299.

Biocompatible Chemically Fueled Transient Polymer Nanoparticles for Temporally Programmable in Vivo Imaging

Biocompatible Chemically Fueled Transient Polymer Nanoparticles for Temporally Programmable in Vivo Imaging

Synthesis and Photoluminescence Mechanism of Multicolored Nitrogen-Doped Carbon Nanodots and Their Application in Polymer Self-Assemblies

Synthesis and Photoluminescence Mechanism of Multicolored Nitrogen-Doped Carbon Nanodots and Their Application in Polymer Self-Assemblies

Dendritic peptide-conjugated polymeric nanovectors for non-toxic delivery of plasmid DNA and enhanced non-viral transfection of immune cells

SummaryPlasmid DNA (pDNA) transfection is advantageous for gene therapies requiring larger genetic elements, including “all-in-one” CRISPR/Cas9 plasmids, but is limited by toxicity as well as poor intracellular release and transfection efficiency in immune cell populations. Here, we developed a synthetic non-viral gene delivery platform composed of poly(ethylene glycol)-b-poly(propylene sulfide) copolymers linked to a cationic dendritic peptide (DP) via a reduceable bond, PEG-b-PPS-ss-DP (PPDP). A library of self-assembling PPDP polymers was synthesized and screened to identify optimal constructs capable of transfecting macrophages with small (pCMV-DsRed, 4.6 kb) and large (pL-CRISPR.EFS.tRFP, 11.7 kb) plasmids. The optimized PPDP construct transfected macrophages, fibroblasts, dendritic cells, and T cells more efficiently and with less toxicity than a commercial Lipo2K reagent, regardless of pDNA size and under standard culture conditions in the presence of serum. The PPDP technology described herein is a stimuli-responsive polymeric nanovector that can be leveraged to meet diverse challenges in gene delivery.

Hierarchically Ordered Perovskites with High Photo‐Electronic and Environmental Stability via Nanoimprinting Guided Block Copolymer Self‐Assembly (Adv. Mater. Interfaces 16/2022)

Hierarchically Ordered Perovskites Hierarchically ordered perovskites are developed by nanoimprinting-guided self-assembly with a block copolymer template as reported in article number 2200082 by Hyowon Han, Cheolmin Park, and co-workers. Highly enhanced photoluminescence with environmental stability is achieved by surface passivated Mie resonance of nanopattern, combined with 10 nm-thick ultrathin self-assembled top skin polymer layer.

Self-Assembly in water of C60 fullerene into isotropic nanoparticles or nanoplatelets mediated by a cationic amphiphilic polymer

HypothesisTo disperse high concentration of C60 fullerene in water, we propose to use an emulsification-evaporation process in the presence of an amphiphilic polymer whose chemical structure has been chosen for inducing specific interaction with fullerene The viscosity enhancement provided by self-assembly of the amphiphilic polymers in water should result in high stability of the suspensions. The organic solvent has also to been chosen so as to maximize the initial fullerene concentration. ExperimentsThe concentrations of polymer and fullerene, the solvent type and the volume fraction of the organic phase have been varied. Their influence on the concentration of the fullerene dispersions and on the size and shape of the resulting nanoparticles have been investigated by UV–Visible spectroscopy, light scattering and cryo-transmission electron microscopy experiments. FindingsThe resulting nanoparticles consist of aggregates of C60 fullerene stabilized by the cationic polymer with morphologies/sizes tunable through fullerene and polymer concentration. At high fullerene concentration, nanoplatelets are obtained that consist in thin 2D nanocrystals. Their suspensions are very stable with time due to the viscosity of the dispersing aqueous medium. The concentration of fullerene nanoparticles dispersed in water is as high as 8 g/L which corresponds to an upper limit that has never been reached so far.

Metal-coordination-driven self-assembly synthesis of porous iron/carbon composite for high-efficiency electromagnetic wave absorption

Hydrophilic-hydrophobic microphase separation is an important mechanism to promote aqueous polymer self-assembly. However, it is rarely used in the construction of magneto-dielectric absorbers in the interdisciplinary research involving organic polymer and inorganic hybrid material. Herein, a novel metal-coordination-driven self-assembly strategy is proposed for fabricating organic–inorganic composite co-assemblies by combining resorcinol–formaldehyde resin as carbon precursor and iron-containing polymer self-assemblies as soft template. Co-assemblies are then transformed into porous iron/carbon (Fe/C) composites with spherical Fe nanoparticles and micro-mesopores that form in graphited carbon matrix through high-temperature pyrolysis. The minimum reflection loss of Fe/C-800 composite in paraffin matrix with 10% filler loading can reach −57.8 dB, while the effective absorption bandwidth of 5.3 GHz can cover the whole X band. It is considered that the co-assemblies-derived microstructure and magneto-dielectric composition contribute to the multiple reflection, polarization loss, conductive loss, ferromagnetic resonance and eddy current loss for high-efficiency electromagnetic wave absorption. In general, this work opens up new prospects for designing and preparing high-performance magneto-dielectric absorbers via a novel metal-coordination-driven self-assembly strategy.

Current Perspectives on Synthetic Compartments for Biomedical Applications.

Nano- and micrometer-sized compartments composed of synthetic polymers are designed to mimic spatial and temporal divisions found in nature. Self-assembly of polymers into compartments such as polymersomes, giant unilamellar vesicles (GUVs), layer-by-layer (LbL) capsules, capsosomes, or polyion complex vesicles (PICsomes) allows for the separation of defined environments from the exterior. These compartments can be further engineered through the incorporation of (bio)molecules within the lumen or into the membrane, while the membrane can be decorated with functional moieties to produce catalytic compartments with defined structures and functions. Nanometer-sized compartments are used for imaging, theranostic, and therapeutic applications as a more mechanically stable alternative to liposomes, and through the encapsulation of catalytic molecules, i.e., enzymes, catalytic compartments can localize and act in vivo. On the micrometer scale, such biohybrid systems are used to encapsulate model proteins and form multicompartmentalized structures through the combination of multiple compartments, reaching closer to the creation of artificial organelles and cells. Significant progress in therapeutic applications and modeling strategies has been achieved through both the creation of polymers with tailored properties and functionalizations and novel techniques for their assembly.

Injectable Thermosensitive Iodine-Loaded Starch-g-poly(N-isopropylacrylamide) Hydrogel for Cancer Photothermal Therapy and Anti-Infection.

Although photothermal therapy (PTT) can effectively eliminate tumors, the normal tissues near tumors are inevitably damaged by heat and infected by bacteria, which greatly limits the therapeutic effect. In this work, an injectable thermosensitive hydrogel based on iodine-loaded starch-g-poly(N-isopropylacrylamide) (PNSI) is developed to overcome this problem. FTIR, 1 H NMR, and UV-vis spectra confirm the graft copolymerization of poly(N-isopropylacrylamide) with starch and the formation of "iodine-starch" complex. Transmission electron microscope images show PNSI polymer self-assembles into regular spherical nanogel with a size of ≈50nm. The concentrated nanogel dispersion is a sol at room temperature and transforms to hydrogel at body temperature. Under NIR laser irradiation for 10min, the ΔT of the nanogel dispersion approachs about 20°C with excellent thermal stability and high cytotoxicity due to the photothermal effect of the "iodine-starch" complex. After intratumor injection, this injectable hydrogel efficiently inhibites the tumor growth under 808nm laser irradiation. Furthermore, it can also suppress Staphylococcus aureus infection in the wound post-PTT due to the release of iodine, which promotes wound healing. Therefore, this injectable thermosensitive "iodine-starch" composite hydrogel with advantages of good biocompatible and easy preparation possesses potential application for tumor photothermal therapy and antibacterial infection.

Development, Characterization, and Antimicrobial Evaluation of Ampicillin-Loaded Nanoparticles Based on Poly(maleic acid-co-vinylpyrrolidone) on Resistant Staphylococcus aureus Strains.

This study was focused on synthesizing, characterizing, and evaluating the antimicrobial effect of polymer nanoparticles (NPs) loaded with ampicillin. For this, the NPs were produced through polymeric self-assembly in aqueous media assisted by high-intensity sonication, using anionic polymers corresponding to the sodium salts of poly(maleic acid-co-vinylpyrrolidone) and poly(maleic acid-co-vinylpyrrolidone) modified with decyl-amine, here named as PMA-VP and PMA-VP-N10, respectively. The polymeric NPs were analyzed and characterized through the formation of polymeric pseudo-phases utilizing pyrene as fluorescent probe, as well as by measurements of particle size, zeta potential, polydispersity index, and encapsulation efficiency. The antimicrobial effect was evaluated by means of the broth microdilution method employing ampicillin sensitive and resistant Staphylococcus aureus strains. The results showed that PMA-VP and PMA-VP-N10 polymers can self-assemble, forming several types of hydrophobic pseudo-phases with respect to the medium pH and polymer concentration. Likewise, the results described that zeta potential, particle size, polydispersity index, and encapsulation efficiency are extremely dependent on the medium pH, whereas the antimicrobial activity displayed an interesting recovery of antibiotic activity when ampicillin is loaded in the polymeric NPs.

Electrostatic self-assembled layered polymers form supramolecular heterojunction catalyst for photocatalytic reduction of high-stability nitrate in water

In this work, two polymers are connected by electrostatic self-assembly method to form a supramolecular heterojunction to remove pollutants. g-C3N4-Cl/PANI catalyst can be used for photocatalytic reduction of nitrate in water, and the nitrogen selectivity reaches 98.2%. Specially, charge density analysis and comparative experiments showed that the introduction of covalent chlorine increased in electron transfer conduction between layers. In addition, differential charge density and solid EPR tests reveal high electron density and electron transfer pathways for supramolecular heterostructures. The results of the work function give direct evidence for the high catalytic performance of the supramolecular heterojunction. The reasons and active species of photocatalytic reduction of nitrate by g-C3N4-Cl and g-C3N4-Cl/PANI are compared. The catalyst exhibits the performance of highly reducing nitrate to harmless nitrogen with the contribution of supramolecular heterojunction and covalent chlorine. In short, a new idea of constructing a supramolecular photocatalyst is proposed, which can be applied to efficiency reduce nitrate in water.

Erythrocyte-biomimetic nanosystems to improve antitumor effects of paclitaxel on epithelial cancers.

Chemotherapy is a difficult treatment for cancer patients because of the low effective accumulation of chemo-drugs and their detrimental side effects. Nanoparticles have shown promise as a solution to these problems. However, the known differences in the porosity and vascularization of tumor vessels, and other factors, including the potential formation of a "protein crown," the short half-life time in circulation, and the low drug distribution, often limit their application. To address these problems, biomimetic nanoparticles coated with cell membranes have been developed and shown to have advantages such as prolonged circulation, high biocompatibility, and enhanced targeting abilities in drugs and nanoparticles, thus exhibiting good application prospects in cancer therapy for liver, lung, and melanoma cancers. Accordingly, we designed a PH-sensitive biomimetic nanodrug delivery system with a delicate "core-shell" structure based on red blood cell membranes. Briefly, core nanoparticles were synthesized by the self-assembly of natural amphoteric polymers, including hydrophilic carboxymethylcellulose sodium and hydrophobic stearic acid. For the shell structure, red blood cell membranes were modified using folic acid by a lipid tether (1,2-distearoyl-sn-glycero-3-phosphoethanolamine) to increase tumor-targeting ability, whereas polyethylene glycol was inserted to decrease lipid tether modification-induced potential sequestration by either the mononuclear phagocyte system or the reticuloendothelial system. Via a series of formulation optimizations, paclitaxel was packaged into the red blood membrane-based core-shell nanoparticles with an average size of 226.9±2.75nm and a negative Zeta potential of -14.5±0.3mV. More importantly, the examinations focusing on CD47, a representative red blood cell membrane protein, revealed not only the successful establishment of the membrane shell but also the right-side-out membrane orientation on our core-shell nanoparticles. Our nanodrug delivery system showed good biocompatibility and sensitivity to acidic tumor microenvironments while effectively prolonging the circulation time of paclitaxel and further enhancing its antitumor effects on epithelial malignancies, including liver, lung, and melanoma cancers. In particular, our nanodrug delivery system significantly alleviated paclitaxel-induced renal toxicity. Taken together, our findings highlight that the red blood membrane-based core-shell nanoparticle is a promising biomimetic nanodrug delivery system for functionally delivering chemotherapeutic drugs, and it has promise in clinical applications.

Hierarchical Self-Assembly and Chemical Imaging of Nanoscale Domains in Polymer Blend Thin Films

Self-assembly of polymers driven by intermolecular and intramolecular interactions leads to rich structural variations in thin films of polymer blends. In this work, ordering of poly(3-hexylthiophene-2,5-diyl) (P3HT) to form nanoparticles (NPs) and the self-assembly pattern of the NPs in poly(4-vinylpyridine) (P4VP) matrix are revealed by using scattering-type scanning near-field optical microscopy (s-SNOM). The P3HT NPs are formed spontaneously when the P3HT/P4VP/chloroform solution is spin-cast on unpatterned silicon wafer at room temperature. We find that the P3HT NPs organize within the P4VP matrix forming continuous stripes along the parallel striations, depending on the solution composition and spin-coating angular speed. The spacing between the parallel P3HT stripes that runs along the center of the ridges varies from sample to sample within 4–12 μm, whereas the width of the P3HT stripes confined within the ridges ranges from 0.2 to 1.1 μm as determined from the s-SNOM infrared phase contrast. The sizes of the P3HT NPs range from 5 to over 100 nm depending on the composition of the blend as determined by using an atomic force microscope after selectively dissolving the P4VP matrix. The smallest size observed in our experiment is significantly smaller than the smallest diameter (larger than 20 nm) reported in the literature. The results presented here show that interaction between immiscible polymers during solvent evaporation can be manipulated to control hierarchical self-assembly from molecular ordering to mesoscale dimensions, and high-resolution chemical imaging is necessary to resolve nanoscale domains so that solution processes can be optimized.

Interfacial Self-Assembly of Amphiphilic Core-Shell Bottlebrush Block Copolymers Toward Responsive Photonic Balls Bearing Ionic Channels.

Photonic balls can be facilely obtained through interfacial self-assembly of amphiphilic bottlebrush block polymers (BBCPs) within a water-in-oil-in-water (w/o/w) multiple emulsion system, and polystyrene (PS) has been employed as the skeleton of the balls showing no responsive properties. Here, the design and synthesis of core-shell BBCPs are demonstrated with a poly(tert-butyl acrylate)-block-polystyrene (PtBA-b-PS) block copolymer as the hydrophobic side chains and poly(ethylene glycol) as the hydrophilic block. Interfacial self-assembly of the core-shell BBCPs within shrinking droplets produces porous microspheres with full-spectrum structural colors through an organized spontaneous emulsification process. The PtBA core wrapped by PS in the skeleton of the balls can be converted into polyacrylic acid (PAA) forming an ionic channel responsive to pH variations. Consequently, the hydrolyzed photonic balls show different colors under different pH conditions dependent on varying degrees of ionization and hydration of the PAA channel. Reflected colors can be verified using an optical spectrometer, providing an effective strategy for precise pH indication.

Light controlled drug-based supramolecular polymer self-assemblies for efficient antibacterial manipulation

The infections and diseases caused by harmful bacteria are regarded as the worldwide health-threatening issue. The most antibiotics-based delivery systems restricted the controlled drug release at specific infection sites due to the stable chemical conjugation, thus largely compromising the treatment effectiveness. Herein, we report the construction of light controlled drug-based supramolecular polymer (LDSP), which is endowed the “switch on” function for realizing the controllable antibiotics released in specific sites. LDSP was first formed based on the host-guest interaction between β-cyclodextrin units grafted hyaluronic acid chain (HA-CD) and azobenzene moiety linked by two enoxacin units (Azo-(Eno)2), and could further self-assemble into light controlled drug-based supramolecular polymer self-assemblies (LDSPSAs). Under the UV light irradiation, the “switch on” function of LDSPSAs could be effectively turned on at the specific infected tissues due to the smartly dissociated host-guest interaction, facilitating the controlled release of the hydrophobic Azo-(Eno)2 to interact with bacteria for efficient antibacterial effect. The biological evaluation demonstrated that LDSPSAs achieved good antibacterial efficiency and well biosafety.

Supramolecular Frameworks and a Luminescent Coordination Polymer from New β-Diketone/Tetrazole Ligands

Mixed multidentate linkers with donor groups of different types can be fruitfully exploited in the self-assembly of coordination polymers (CPs) and Metal-Organic Frameworks (MOFs). In this work we develop new ligands containing a β-diketone chelating functionality, to better control the stereochemistry at the metal center, and tetrazolyl multidentate bridging groups, a combination not yet explored for networking with metal ions. The new ligands, 1,3-bis(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H3L1) and 1-phenyl-3-(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H2L2), are synthesized from the corresponding nitrile precursors by [2+3] dipolar cycloaddition of azide under metal-free catalytic conditions. Crystal structure analysis evidences the involvement of tetrazolyl fragments in multiple hydrogen bonding giving 2D and 1D supramolecular frameworks. Reactivity of the new ligands with different metal salts indicates good coordinating ability, and we report the preparation and structural characterization of the tris–chelate complex [Fe(HL1)3]3− (1) and the homometallic 2D CP [ZnL2(DMSO)] (2). In compound 1 only the diketonate donor is used, whereas the partially deprotonated tetrazolyl groups are involved in hydrogen bonding, giving rise to a 2D supramolecular framework of (6,3)IIa topological type. In compound 2 the ligand is completely deprotonated and uses both the diketonate donor (chelating) and the tetrazolate fragment (bridging) to coordinate the Zn(II) ions. The resulting neutral 2D network of sql topology shows luminescence in the solid state, which is red shifted with respect to the free ligand. Interestingly, it can be easily exfoliated in water to give a luminescent colloidal solution.

Macrocycle-Surfaced Polymer Nanocapsules: An Emerging Paradigm for Biomedical Applications.

In the recent decade, macrocycle-surfaced polymer nanocapsules have been developed and studied as potential drug carriers. In particular, a unique group of these nanocapsules were constructed from a covalently self-assembled polymer network based on several classic macrocycles including cucurbituril, pillararene, and calixarene. The unique structure of these nanocapsules consists of a liquid or solid core and a shell laced with macrocycles in which the macrocycles not only act as the shell matrix of the nanocapsules but also allow further facile, modular functionalization via host-guest interactions with guest-tagged molecules. More interestingly, when a responsive cross-linker was introduced between the macrocycles, the payload inside the nanocapsules could be selectively released in the presence of typical hallmarks of certain diseases, which is of great interest for biomedical applications. In this Topical Review, macrocycle-surfaced polymer nanocapsules derived from covalently self-assembled polymer networks are introduced systemically with a focus on the molecular design and biomedical applications.

2+2] Cyclo-Addition Reactions for Efficient Polymerization on a HOPG Surface at Ambient Conditions.

Polymers obtained by on-surface chemistry have emerged as a class of promising materials. Here, we propose a new strategy to obtain self-assembled 1D polymers by using photochemical [2+2] cyclo-addition or by using a mild thermal annealing. All nanostructures are fully characterized by using scanning tunneling microscopy at ambient conditions on a graphite surface. We demonstrated that nature of the stimulus strongly alters the overall quality of the resulting polymers in terms of length and number of defects. This new way is an efficient method to elaborate on-surface self-assembled 1D polymers.