Polymer Chemistry Blog

In this paper, Huang, Guo and co-workers developed a novel micellar cross-linking copolymerization method to prepare highly stretchable and resilient hydrogels. The polymerization was based on free-radical copolymerization of water soluble acrylamide and a polymerizable macromolecular surfactant (i.e., amphiphilic polyurethane macromonomer) which can self-assemble into micelles acting as multifunctional cross-linkers. The mechanical properties, such as breaking elongation ratio, modulus and fracture toughness can be easily adjusted by varying the concentration of the polymerizable macromolecular surfactants. In addition, the mechanical energy storage efficiency (also known as resilience) was more than 96% at a strain up to 400%. These findings established a strategy for the preparation of hydrogels that combine high extendibility with excellent resilience and may greatly benefit the further use of hydrogels in tissue engineering and other soft materials research fields.

Highly stretchable and resilient hydrogels from the copolymerization of acrylamide and a polymerizable macromolecular surfactant by Mei Tan, Tingting Zhao, He Huang and Mingyu Guo Polym. Chem. 2013, 4, 5570-5576.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

In this article, Stenzel and co-workers designed three different macromolecular Pt-drugs using Cu-click chemistry to attach a bidentate amino ligand to the polymer. Two statistical copolymers with different ligand densities were prepared, which were compared to the block copolymer. DNA binding studies revealed that the statistical copolymer with the highest density of Pt-drugs had the highest affinity to the DNA, due to a multivalent effect. Interestingly, when evaluating the cytotoxic effect of these macromolecular drugs using OVCAR-3 cells the activities of all three polymer architectures were similar. It can therefore be concluded that although DNA binding tests may give an initial indication on the ability of the structure to bind to the DNA, they cannot predict the outcome.

Macromolecular platinum-drugs based on statistical and block copolymer structures and their DNA binding ability by Khairil Juhanni Abd Karim, Sandra Binauld, Wei Scarano and Martina H. Stenzel Polym. Chem. 2013, 4, 5542-5554.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

In this context, Tao, Wei and co-workers have revisited the Biginelli reaction as a potential tri-component click chemistry. Through the quick and efficient modification of polymer side groups and locking of two polymer chains, Biginelli-type homopolymers and Biginelli-locked copolymers can be facilely and quantitatively obtained. Moreover, the Biginelli reaction showed good compatibility with RAFT polymerization to construct a one-pot MCP system. Both reactions proceeded well without interference, and almost neat Biginelli functionalized homopolymers were successfully achieved in a one-pot fashion. More importantly, the Biginelli reaction can also be recognized as a ‘catalyst-free’ bioorthogonal-click reaction, through which a fluorescent probe can be covalently anchored onto cell membranes without external addition of a catalyst, implying the potential application of the Biginelli reaction in chemical biology.

A new insight into the Biginelli reaction: the dawn of multicomponent click chemistry? by Chongyu Zhu, Bin Yang, Yuan Zhao, Changkui Fu, Lei Tao and Yen Wei Polym. Chem. 2013, 4, 5395-5400.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

In their paper, Leclerc and co-workers reported the preparation of N-octylthieno[3,4-c]pyrrole-4,6-dione with 4,4-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole (PDTSiTPD) and 4,4-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]germole (PDTGeTPD), which have exhibited high efficiencies in organic solar cells, using direct (hetero)arylation polymerization methodologies. In order to circumvent side reactions leading to cross-linked polymers, a number of new dithieno[3,2-b:2′,3′-d]silole (DTSi) monomers were prepared where the β-positions were blocked with alkyl chains and the alkyl groups on the heteroatom were modified. Co-polymers were synthesized with N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) and the oxygen congener, N-alkylfuro[3,4-c]pyrrole-4,6-dione (FPD).

Direct heteroarylation of β-protected dithienosilole and dithienogermole monomers with thieno[3,4-c]pyrrole-4,6-dione and furo[3,4-c]pyrrole-4,6-dione by Lauren G. Mercier, Badrou Réda Aïch, Ahmed Najari, Serge Beaupré, Philippe Berrouard, Agnieszka Pron, Amélie Robitaille, Ye Tao and Mario Leclerc Polym. Chem. 2013, 4, 5252-5260.

This article is part of the Polymer Chemistry themed collection on Conjugated polymers.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

In their study, Iyer and co-workers synthesized a non toxic conjugated polymer, poly(1,4-bis-(8-(8-hydroxyquinoline)-octyloxy)-benzene) (PHQ), able to bind iron containing heme and non-heme proteins, such as ferritin, at nanomolar levels with the highest known selectivity in cerebrospinal fluid (CSF). It has been employed to interact with the bound iron, including non-heme ferritin, in the Ab protofibril aggregates and to diminish their accumulation. The anti-AD activity of PHQ was confirmed via in vitro control studies by doping CSF of healthy individuals with Ab(1–40) with and without iron using a Thioflavin-T binding assay test and electron microscopy analysis. This new strategy to clear the cerebral deposits using conjugated polymers enables the toxic aggregated Ab peptide fibrils present in the CSF to be successfully disrupted under physiological conditions.

A rapid and sensitive detection of ferritin at a nanomolar level and disruption of amyloid β fibrils using fluorescent conjugated polymer by B. Muthuraj, Sameer Hussain and Parameswar Krishnan Iyer, Polym. Chem. 2013, 4, 5096-5107 .

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

In the present study, Connal and co-workers established a versatile strategy to prepare a diverse range of self-assembled colloidal nanostructures from the same hydrophobic BCP.  Polymer nanoparticles with well-ordered phase separated morphology were accessed from the solution self-assembly of a hydrophobic polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCP. However, the introduction of a hydrophilic guest capable of hydrogen bonding with the pyridine block resulted in an amphiphilic BCP, thus drastically altering the self-assembly behavior and leading to traditional spherical micelles in water. Furthermore, a hydrophobic guest was incorporated into the BCP which formed internally nanostructured assemblies in water with the hydrophobic guest entrapped within the nanoparticle. Their methodology can be used to engineer new systems that incorporate and release guests upon triggered disruption of the supramolecular bonds. Furthermore, the diversity of nanostructures that can be tuned by the incorporation of different guests enables opportunities for outstanding control of the nanoparticle properties.

Supramolecular guests in solvent driven block copolymer assembly: from internally structured nanoparticles to micelles by Daniel Klinger, Maxwell J. Robb, Jason M. Spruell, Nathaniel A. Lynd, Craig J. Hawker and Luke A. Connal, Polym. Chem. 2013, 4, 5038-5042.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

Inspired by the success of polymer-composite materials in replacing metals across a range of high value products, Hayes and co-workers have investigated the possibility of producing nanoparticle-reinforced, supramolecular, healable composites. The material comprises a blend of three components: a pyrene-functionalized polyamide, a polydiimide and pyrene-functionalized gold nanoparticles (P-AuNPs). The polymeric components interact by forming well-defined π–π stacked complexes between π-electron rich pyrenyl residues and π-electron deficient polydiimide residues. Complexation studies in solution demonstrate that the introduction of P-AuNPs results in more rapid formation of an insoluble supramolecular network when compared to control samples that did not contain the P-AuNPs. Films of the nanocomposite are tough and flexible, and contain a relatively homogeneous dispersion of P-AuNPs. Films containing P-AuNPs are stronger and stiffer than those cast from the same polymers but without P-AuNPs, and also than films containing AuNPs that lacked the pyrenyl motif. Healing studies using a classic break/heal test, followed by stress–strain analysis, showed that materials containing up to 10 wt% P-AuNPs can even exhibit healing efficiencies of more than 100%.

Molecular recognition between functionalized gold nanoparticles and healable, supramolecular polymer blends – a route to property enhancement by Rajendran Vaiyapuri, Barnaby W. Greenland, Howard M. Colquhoun, Joanne M. Elliott and Wayne Hayes, Polym. Chem. 2013, 4, 4902-4909.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

Albumin-based drug delivery has been demonstrated to be useful for achieving improved cancer therapy, largely due to its passive target toward tumor via the enhanced permeability and retention effect and the increased demand for albumin by tumor cells as source of energy and amino acids. However, albumin lacks not only the active mechanism to overcome the cell membrane barrier, but also the ability to penetrate into tumor tissues. Herein, a cell-penetrating albumin-based delivery strategy was developed, in which a cell-penetrating peptide was chemically conjugated to albumin in order to enhance the efficiency of intracellular delivery and tumor penetration. Doxorubicin (DOX) molecules were loaded into the carrier via cleavable disulfide bonds, which are responsive to the highly reducing environment in the cytosol of tumor cells, thus archiving prodrug-type targeted drug release. The cell-penetrating albumin–DOX conjugates displayed significantly higher antitumor activity than DOX. More interestingly, the conjugates also efficiently killed the drug-resistant tumor cells, in sharp contrast to the ineffective DOX. The studies with human xenograft tumors in nude mice further demonstrated the enhanced antitumor efficacy and reduced side effects of the cell-penetrating albumin-assisted DOX delivery strategy, indicating the promise of this delivery system.

The ring-opening polymerization of cyclic ketene acetals (CKAs) by controlled radical mechanisms represents an alternative route for the synthesis of aliphatic polyesters. For the first time, 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) and 2-methylene-4-phenyl-1,3-dioxolane (MPDL) were homopolymerized by nitroxide mediated polymerization (NMP), from the commercially available SG1-based BlocBuilder MA alkoxyamine. Various experimental conditions (i.e., reaction temperature, nature of solvent, and nature of the alkyl initiating radical) were varied to determine the optimized conditions in terms of polymerization kinetics and living character of the final polymer. Chain-end extensions from either PS-SG1 or PBMDO-SG1 were also performed in order to furnish PS-b-PBMDO and PBMDO-b-PS, respectively, thus demonstrating the synthesis of block copolymers comprising a CKA block. In order to have a better insight into the polymerization mechanism, the occurrence of side reactions was analyzed by ³¹P NMR spectroscopy and ESI-MS. It was supposed that the ketal-based macroradical could be irreversibly trapped by nitroxide and thus the corresponding macroalkoxyamine decomposed by CO–N bond dissociation. DFT calculations as well as PREDICI modeling were also undertaken in order to support this hypothesis.

2-Methacryloyloxyethyl-phosphorylcholine (MPC) polymers are zwitterionic in character and are widely used in a range of biomedical devices. The availability of facile polymerization approaches has allowed the synthesis of well-defined MPC polymers, which are now used as delivery carriers for in vitro and in vivo applications. Although biocompatibility testing has extensively been performed on insoluble MPC-based materials, to the best of our knowledge, there are no reports on the hemocompatibility of soluble MPC polymers. Therefore, in this work, linear and hyperbranched MPC polymers of varying molecular weights are synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. The polymers produced are studied for their blood compatibility, as a function of their molecular weights and structures (linear versus hyperbranched). The hemocompatibility studies including clot formation, complement and platelet activation, and hemolysis indicate that linear and hyperbranched MPC polymers are blood compatible. The remarkable difference in erythrocyte aggregation in the presence of linear and branched MPC polymers indicates the importance of the branched polymer architecture.