Polymerization-Induced Self-Assembly of Galactose-Functionalized Biocompatible Diblock Copolymers for Intracellular Delivery

Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition–fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo

Combination of Fluorine and Tertiary Amine Activation in Catalyst-Free Thia-Michael Covalent Adaptable Networks

A series of catalyst-free covalent adaptable networks (CANs) have been developed using a reversible thia-Michael reaction activated by fluorine atom substitution and by an intramolecular tertiary amine. The thia-Michael exchange rate was first evaluated by a preliminary molecular study coupled to density functional theory (DFT) calculations. This study enabled us to highlight the necessity of combining fluorine and tertiary amine activation to observe the thia-Michael exchange. Then, by modulating the structure, nature, and functionality of the thiol monomers, a wide range of mechanical properties and thermal properties were achieved. Relationships between the monomer structure and the dynamic properties were also highlighted through the dynamic study of these materials. Finally, the ability of the fluorinated thia-Michael CANs to be reprocessed was assessed by thermal and mechanical analyses of up to three reshaping cycles

Importance of Microstructure Control for Designing New Electroactive Terpolymers Based on Vinylidene Fluoride and Trifluoroethylene

A new family of electroactive fluorinated terpolymers of vinylidene fluoride (VDF), trifluoroethylene (TrFE) and 3,3,3-trifluoropropene (TFP) is presented. Statistical poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-TFP) terpolymers with a VDF/TrFE molar ratio of <i>ca</i>. 65/35 and a TFP composition ranging from 0 to 10 mol % were prepared in high yields by free radical terpolymerization in dimethyl carbonate (DMC), initiated by a symmetrical peroxydicarbonate initiator. The choice of TFP as a termonomer was driven by the potential property of the CF₃ side groups to limit crystal growth and potentially favor the formation of nanodomains known to enhance electrostrictive properties. For the first time, the reactivity ratios of the TrFE/TFP (<i>r</i>_TrFE = 0.13 and <i>r</i>_TFP = 3.72 at 48 °C) couple were determined using the Kelen–Tudos linear method, and used in combination with VDF/TrFE and VDF/TFP reactivity ratios to better understand the structures of the terpolymers. Detailed ¹H and ¹⁹F solution NMR spectroscopic studies were performed and afforded the in-depth characterization of the terpolymers microstructures. The examination of the terpolymer’s composition as a function of the three monomers conversions revealed a strong structural heterogeneity where a 62/33/5 VDF/TrFE/TFP initial monomer composition resulted in a 47/11/42 poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-TFP) terpolymer at low conversion. It was indeed found that TFP preferentially homopolymerizes despite its low initial concentration. The influence of the TFP units on the thermal transitions (<i>T</i>_Curie = 65 °C and <i>T</i>_m = 148 °C for a 67/28/5 poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-TFP) terpolymer), thermal stability and electroactivity (E_c = 63 MV/m at 150 MV/m) was also examined. The combination of the determination of the monomers’ reactivity ratios of the terpolymer microstructures and of the assessment of the physical properties of the terpolymers provided insights on the structure–property relationship of the poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-TFP) terpolymers

Deeper Insight into the MADIX Polymerization of Vinylidene Fluoride

Controlled radical polymerization protocols for vinylidene fluoride (VDF) are still very elusive. MADIX polymerization of VDF has very rarely been reported. The synthesis of PVDF using MADIX solution polymerization was thus investigated in detail. More efficient protocols for solution polymerization were developed and afforded relatively well-defined PVDF. Careful polymer chain-end monitoring using MALDI-TOF as well as ¹H, ¹⁹F, and HETCOR ¹H–¹⁹F NMR revealed that VDF reverse additions and transfer to solvent reactions severely affect the control of the polymerization. Indeed, these unwanted reactions are responsible for a non-negligible loss of CTA and for the accumulation of nonreactive polymer chains in the reaction medium. MADIX polymerization lead to the synthesis of PVDF with high chain-end functionality. However, these PVDF chains cannot reinitiate the polymerization of VDF. This work is the first comprehensive study of the MADIX solution polymerization of VDF

Combination of Cationic and Radical RAFT Polymerizations: A Versatile Route to Well-Defined Poly(ethyl vinyl ether)-<i>block</i>-poly(vinylidene fluoride) Block Copolymers

Poly­(vinylidene fluoride)-containing block copolymers are difficult to prepare and still very rare in spite of their potential use in high added value applications. This communication describes in detail the synthesis of unprecedented poly­(ethyl vinyl ether)<i>-<i>block</i>-</i>poly­(vinylidene fluoride) (PEVE<i>-<i>b</i>-</i>PVDF) block copolymers (BCP) via the sequential combination of cationic RAFT polymerization of vinyl ethers and radical RAFT polymerization of vinylidene fluoride (VDF). Dithiocarbamate chain transfer agents were found to efficiently control the radical RAFT polymerization of VDF and to be suitable for the preparation of PEVE<i>-<i>b</i>-</i>PVDF BCP. These new block copolymers composed of incompatible polymer segments may find applications owing to their phase segregation and self-assembly behavior

Influence of <i>trans</i>-1,3,3,3-Tetrafluoropropene on the Structure–Properties Relationship of VDF- and TrFE-Based Terpolymers

<i>trans</i>-1,3,3,3-Tetrafluoropropene (1234ze) was copolymerized under free radical conditions with vinylidene fluoride (VDF) and trifluoroethylene (TrFE), for the first time, leading to statistical poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-1234ze) electroactive terpolymers. The reactivity ratios of the three comonomer couples were determined (<i>r</i>_VDF = 0.77; <i>r</i>_TrFE = 0.32), (<i>r</i>_VDF = 1.67; <i>r</i>_1234ze = 0.00), and (<i>r</i>_TrFE = 7.56; <i>r</i>_1234ze = 0.00), at 48 °C, using the nonlinear fitting Mayo–Lewis method. 1234ze was shown to be regularly incorporated in the terpolymer chains over the entire course of the reaction providing terpolymer chains with statistical monomer distribution and almost constant composition. These new VDF/TrFE-based terpolymers were characterized by ¹H and ¹⁹F liquid state NMR spectroscopy. The characteristic NMR signals of the VDF–1234ze dyads were identified by comparing the NMR spectral signatures of a poly­(VDF₈₂-<i>co</i>-1234ze₁₈) copolymer and of a terpolymer. The thermal and electroactive properties of poly­(VDF-<i>ter</i>-TrFE-<i>ter</i>-1234ze) terpolymers, with 1234ze content ranging from 0 to 6 mol % and molar masses above 55 kg/mol, were assessed. The randomly distributed 1234ze termonomer units induced the decreases of both the Curie and the melting temperatures of the terpolymer even at low termonomer content (<i>T</i>_Curie = 70 °C and <i>T</i>_m = 126 °C and <i>T</i>_Curie = 72 °C and <i>T</i>_m = 150 °C; for a poly­(VDF₆₉-<i>ter</i>-TrFE₂₈-<i>ter</i>-1234ze₃) terpolymer and a poly­(VDF₆₅-<i>co</i>-TrFE₃₅) copolymer, respectively). Films of the terpolymers were cast, and their electroactive properties were examined by D–E loops measurements. They showed that the presence of 1234ze decreased the remnant polarization (<i>P</i>_r = 45 mC/m² for a poly­(VDF₆₅-<i>co</i>-TrFE₃₅) copolymer to 28 mC/m² for a poly­(VDF₆₉-<i>ter</i>-TrFE₂₅-<i>ter</i>-1234ze₆) terpolymer) probably because it also decreased the crystallinity of the terpolymer. The combination of the studies of the reactivity of the monomers, of the terpolymer microstructures, and of the assessment of their physical properties provides insights into their structure–property relationship

Stretching-Induced Relaxor Ferroelectric Behavior in a Poly(vinylidene fluoride-<i>co</i>-trifluoroethylene-<i>co</i>-hexafluoropropylene) Random Terpolymer

Relaxor ferroelectric (RFE) polymers exhibiting narrow hysteresis loops are attractive for a broad range of potential applications such as electric energy storage, artificial muscles, electrocaloric cooling, and printable electronics. However, current state-of-the-art RFE polymers are primarily poly­(vinylidene fluoride-<i>co</i>-trifluoroethylene-<i>co</i>-X) [P­(VDF-TrFE-X)] random terpolymers with X being 1,1-chloro­fluoroethylene (CFE) or chloro­trifluoroethylene (CTFE). Potential dehydrochlorination at elevated temperatures can prevent the melt-processing of these Cl-containing terpolymers. It is desirable to achieve the RFE behavior for Cl-free terpolymers such as P­(VDF-TrFE-HFP), where HFP stands for hexafluoro­propylene. Nonetheless, HFP units were mostly excluded from the crystalline structure because of their large size, and thus no RFE behavior was observed when crystallized from the quiescent melt. Intriguingly, mechanical stretching could effectively pull the HFP units into the P­(VDF-TrFE) crystals, forming nanosized ferroelectric (FE) domains with a strong physical pinning effect. Consequently, the RFE behavior was observed for the uniaxially stretched P­(VDF-TrFE-HFP) film. Thermal annealing above the Curie temperature (ca. 50 °C) without tension led to the return of the normal FE behavior with broad hysteresis loops. However, thermal annealing above Curie temperature under tension prevented the exclusion of HFP units from the crystalline structure, and thus relatively stable RFE behavior was achieved. Various characterization techniques were utilized to unravel the structure–property relationships for these P­(VDF-TrFE-HFP) films. In addition, the RFE behavior of P­(VDF-TrFE-HFP) was compared to those of other terpolymers. This study provides a unique and simple strategy solely based on film processing to achieve the RFE behavior for P­(VDF-TrFE)-based terpolymers

Utilization of Catechol End-Functionalized PMMA as a Macromolecular Coupling Agent for Ceramic/Fluoropolymer Piezoelectric Composites

An approach based on the use of a macromolecular coupling agent and the aim to improve the interfacial adhesion between piezoelectric ceramics and piezoelectric polymer matrix in piezoelectric composites is presented. Poly(methyl methacrylate) (PMMA) bearing a catechol moiety was used as a macromolecular coupling agent, as it is known to be miscible to piezoelectric fluoropolymers and catechol groups can strongly bind to a large variety of surfaces. Thus, entanglement between the PMMA chains and the amorphous segments of the fluoropolymer would ensure the desired interfacial adhesion. Well-defined PMMA was synthesized via RAFT polymerization using 2-cyano-2-propyl dodecyl trithiocarbonate as a chain-transfer agent. The PMMA ω-chain end was then functionalized with a catechol group via a one-pot aminolysis/thia-Michael addition procedure using a dopamine acrylamide (DA) derivative as a Michael acceptor. The presence of the catechol moiety at the chain end of PMMA was controlled by 1H NMR and cyclic voltammetry measurements. The resulting PMMA-DA was then grafted onto the surface of a lead-free piezoelectric ceramic film (i.e., a thin film of H2O2-activated (Bi0.5Na0.5)TiO3 (BNT) with a large contact area). The increase of the water contact angle confirmed the efficiency of the grafting. A commercial piezoelectric copolymer P(VDF-co-TrFE) was then spin-coated onto the modified BNT surface to form a bilayer composite. The composite cross section prepared by cryofracture was examined by scanning electron microscopy and revealed that the ceramic/polymer interface of the BNT-PMMA/P(VDF-co-TrFE) bilayer composite exhibits a much better cohesion than its counterpart composite prepared from nonmodified BNT. Moreover, the grazing incidence wide-angle X-ray scattering confirmed that the copolymer crystal structure was not impacted by the presence of the PMMA-DA coupling agent. A strong piezoelectric response was locally detected by piezoresponse force microscopy. This study highlights the potential of PMMA-DA as a macromolecular coupling agent to improve the ceramic/polymer interface in piezoelectric composite materials