Telechelic Research Articles

Semi–fluorinated arylene vinylene ether (FAVE) telechelic polymers from polycyclic aromatic hydrocarbon bisphenols and trifluorovinyl aryl ethers

Semi-fluorinated arylene vinylene ether (FAVE) telechelomers and their chain extended PFCB polymers were synthesized via base catalyzed step-growth polymerization of polycyclic aromatic hydrocarbon (PAH) bisphenols and commercially available 4,4ꞌ-bis(4-trifluorovinyloxy)biphenyl (TFVE-BP) monomer. Soluble polymers were obtained in good yield, gave transparent free-standing films, and were characterized by 19F NMR, TGA, DSC, GPC, water contact angle and AFM. Thermal analysis by differential scanning calorimetry (DSC) revealed Tg values ranging from 150 to 168 °C. The new polycyclic aromatic FAVE polymers possess intact trifluorovinyl ether (TFVE) end groups susceptible to thermal chain extension leading to perfluorocyclobutyl (PFCB) aryl ether polymers with Tg ranging from 149 to 174 °C. Semi-fluorinated telechelic polymers with controlled terminal and enchained unsaturation with latent crosslinking ability may find use in specialty applications such as photonics or gas separation technologies.

Sequence effects on internal structure of droplets of associative polymers

Intrinsically disordered proteins (IDPs) can form liquid-like membraneless organelles, gels, and fibers in cells and in vitro. In this study, we propose a simple model of IDPs as associative polymers in poor solvent and explore the formation of transient liquid droplets and their transformation into solid-like aggregates. We use Langevin dynamics simulations of short polymers with two stickers placed symmetrically along their contour to study the effect of the primary sequence of these polymers on their organization inside condensed droplets. We observe that the shape, size, and number of sticker clusters inside the droplet change from a long cylindrical fiber to many compact clusters as one varies the location of stickers along the chain contour. Aging caused by the conversion of intramoleclular to intermolecular associations is observed in droplets of telechelic polymers but not for other sequences of associating polymers. The relevance of our results to condensates of IDPs is discussed.

Programming Self-Assembly and Stimuli-Triggered Response of Hydrophilic Telechelic Polymers with Sequence-Encoded Hydrophobic Initiators

A recent communication from our laboratory demonstrated that the presence of a small hydrophobic initiator residue (core) in water-soluble telechelic dibromo homopolymers can drive their self-assem...

Linear Coordination Polymer Synthesis from Bis-Catechol Functionalized RAFT Polymers.

Catechol-Fe(III) complexes contain some of the strongest known metal-chelate coordination bonds. Despite this, they have until now not been utilized in (polymeric linker) linear coordination polymer (LCP) synthesis. With the view of generating catechol end-functional polymers, a new, symmetrical bis-catechol functionalized trithiocarbonate reversible addition fragmentation chain transfer (RAFT) agent is synthesized (CatDMAT). Acrylamide (AM) and dimethylacrylamide (DMA) polymerizations are conducted with CatDMAT using direct photoactivation RAFT polymerization to yield bis-catechol end-functionalized homo- and block-copolymers of molecular weight 10-15kDa. Catechol-Fe(III) LCPs are successfully formed from the telechelic catechol polymers by bis-complexation to Fe(III). The tetrahedral bis-complex is detected by UV-vis spectroscopy (λmax = 570nm), while increases in relative viscosity and Mn,GPC over their respective uncomplexed polymers confirm the occurrence of supramolecular polymerization. The catechol-LCPs are shown to undergo oxidation and crosslinking in aqueous solution after 24 h.

Self-organization in suspensions of telechelic star polymers

The functionalization of telechelic star polymers (TSPs) bears the opportunity to obtain many different supramolecular structures and respective dynamic responses by controlling well-defined parameters such as the properties of functional groups, the arm number of the stars, the polymer flexibility. Hence, we employ both multiparticle collision dynamics and molecular dynamics simulations to investigate the self-organized network structures of TSPs by varying end-attraction strength, arm number, attractive end-group size and polymer flexibility. The equilibrium properties of end-functionalized TSP suspensions have been investigated. The structural properties change abruptly in the vicinity of end-attraction strength εLJ=3.5kBT for flexible TSPs and εLJ=3kBT for semiflexible and rigid TSPs. The coordination number is defined as the number of end-beads in close proximity of each other. The distribution of the coordination number is more uniform and narrower for stronger end-attractions. The coordination number decreases and the number of free end-beads increases with the increase of arm number for relatively rigid TSPs, and the diffusivity decreases as arm number increases. The coordination number increases with increasing attractive end-group size, while the number of free end-beads decreases. Finally, we find the semiflexible and rigid TSP suspension systems are anisotropic ones for strong end-attractions, relatively small arm numbers and big end-group sizes. We suppose this work could lead experimental researchers to design and develop new biological materials with complex architectures.

Structure Factor of Charged Microemulsion Nanodroplets Decorated with Telechelic Polymers: Experimental and Numerical Study

We investigate thermodynamic and structural properties of positively charged O/W microemulsion spherical nanodroplets, suspended in salt water and decorated with telechelic polymers PEO-m and PEO-2m at low and high volume fraction F (6.98%, 26.5%) by using Small Angle Neutron Scattering (SANS). We describe and propose an effective pair potential interaction between charged colloidal particles in solution both with and without added telechelic polymers PEO-m or PEO-2m.We solve Ornstein-Zernicke (OZ) integral equation in the Hypernetted Chain (HNC) closure relation to obtain the pair correlation function g(r) and the structure factor S(q). A good agreement is found between the experimental and numerical spectra assuming the interaction potentials to be the sum of attractive and repulsive contributions in terms of decoration or bridging of the nanodroplets by the PEO polymer chains.

Self‐assembly of telechelic polymers bearing adamantane groups via host‐guest inclusion complexes with cyclodextrin polymer

AbstractSelf‐assembly and supramolecular inclusion complexations between telechelic polymers bearing one or double adamantane groups and linear poly(β‐cyclodextrin) (P(β‐CD)) were investigated in water. An adamantane (Ada) attached to poly (acrylic acid) (PAA) was prepared by reversible addition‐fragmentation chain transfer polymerization using s‐1‐dodecyl‐s″ ‐(α,α′‐dimethyl‐α″‐acetic acid) trithio‐carbonate functionalized Ada with tert‐butyl acrylate, followed by functional modification. Additionally, two Ada groups capped triblock copolymer F127 were obtained via an esterification reaction. The dynamic light scattering, transmission electron microscope and 1H 2D NOSEY NMR spectroscopy were conducted to characterize the self‐assembly behaviors. With the inclusion complexation of Ada/CD in 1:1 M ratio in water, the spherical micelles were enlarged at 25°C than that of the adamantyl polymer precursors. Due to the PPO segment of Ada‐F127‐Ada, the micelles aggregation showed temperature dependence from 4 to 37°C for precursor and corresponding inclusion complexation; while in Ada‐PAA/P(β‐CD) system, the hydrodynamic diameters decreased with pH decreasing.

Tale of Two Tails: Molecular Exchange Kinetics of Telechelic Polymer Micelles.

Telechelic polymers contain two chain ends that are able to promote self-assembly into "flowerlike" or interconnected micellar structures. Here, we investigate the molecular exchange kinetics of such micelles using time-resolved small-angle neutron scattering. We show that the activation energies of monofunctional and telechelic chain exchange are identical. This demonstrates that the two chain ends are not simultaneously released in a single event. Instead, the results show that, contrary to regular micelles, the kinetics occurs in a multistep process involving a collision-induced single-molecule exchange mechanism where the exchange rate is directly proportional to the polymer concentration. We show that this novel mechanism can be quantitatively explained by a simple kinetic model.

End-Group Chemistry and Junction Chemistry in Polymer Science: Past, Present, and Future

The current goal in functional polymeric material research is the preparation of polymers with high-fidelity nanoscale self-assembled structures and advanced functionality. Thus, recent research efforts have focused on linking chemistry for the development of tailor-made polymers with desired properties. The design of α- or ω-functionalized telechelic polymers with strongly associative interactions is connected to their unique supramolecular self-assembly behavior in homopolymers and blends. In addition, the end-group modification of block copolymers has shown to alter the polymer morphology radically, resulting in unprecedented property changes arising from confinement effects. This is fascinating because the content of terminal moieties is small compared to that of macromolecular polymer backbones. As an emerging theme in polymer designs and end-group chemistry, the controlled synthesis of polymers with complex architectures and functional linkages has been performed extensively in the past few decades....

Molecular simulation of networks formed by end-linking of tetra-arm star polymers: Effects of network structures on mechanical properties

The structures and the mechanical properties of networks formed by end-linking of two types of tetra-arm star polymers are studied by a coarse-grained molecular dynamics simulation. The formation efficiency of elastically effective chains is improved by increasing the length of the arms and the volume fraction of the star polymers at the preparation stage. When the uniaxial elongation is applied to the networks in the as-prepared state, the shear modulus is proportional to the number density of the elastically effective chains and indicates an intermediate value between the phantom and affine network models. In the equilibrium swollen state, the shear moduli of the networks prepared at high volume fractions are significantly enhanced by trapped entanglements. The networks formed from the tetra-arm star polymers show higher number densities of the elastically effective chains than networks consisting of telechelic functional polymers and cross-linkers.

Telechelics Based on Catalytic Alternating Ring-Opening Metathesis Polymerization.

We describe a protocol to synthesize alternating telechelic ROMP copolymers of 7-oxa-norbornene derivatives and cycloalkenes under catalytic conditions. These copolymers were synthesized using Grubbs' second-generation catalyst. The sterically less hindered backbone double bonds of the resulting alternating copolymers facilitate the chain transfer (secondary metathesis) reactions. In the presence of symmetrical chain transfer agents (CTA), alternating copolymers could be synthesized catalytically. This procedure allows the synthesis of telechelic polymers based on potentially functional 7-oxa-norbornene derivatives under thermodynamic equilibrium conditions. The molar mass of the alternating copolymer was controlled by the monomer to CTA ratio. The end group of the copolymers synthesized in the catalytic manner was addressed by the CTA functionality, yielding telechelic copolymers in excellent yields. 1H NMR spectroscopy, MALDI-ToF mass spectrometry, and SEC analysis confirmed the chemical identity of the alternating telechelic copolymers with excellent control over the molar mass.

Synthesis of telechelic PNIPAM ended with 9,10-dihydroacridine group as a recyclable and specific Fe3+ detection fluorescent sensor

A novel telechelic Poly(N-isopropylacrylamide) ended with 4'-(9,10-diphenyl- 9,10-dihydropyridine-9-yl)-[1,1′-biphenyl]-4-amine (DPDHR-NH2) group named as DPDHR-PNIPAM, was designed and synthesized to be used as a potential recyclable Fe3+ ion detective fluorescent sensor. Firstly, DPDHR-NH2 as the central part of the fluorescent sensor was synthesized to react with 2-bromoisobutyryl bromide to form initiator. Then, N-isopropylacrylamide as a monomer was initiated by 2-bromo-N-(4'-(9,10-diphenyl-9,10-dihydroacridin-9-yl)-[1,1′-biphenyl]-4-yl)-2-methylpropanamide (DPDHR-Br) to polymerize into telechelic polymer DPDHR-PNIPAM through atom transfer radical polymerization (ATRP). Lastly, DPDHR-PNIPAM was carefully characterized by FTIR, 1H NMR, elemental analysis, GPC, and UV–vis. At room temperature, DPDHR-PNIPAM displayed high-water solubility, highly specific and sensitive towards Fe3+ detection as low as 1.32 × 10−6 M. The selectivity of DPDHR-PNIPAM toward Fe3+ ion experiment showed it was a turn-off fluorescence response in multi-ion-mixed solution. As a thermosensitive polymer, above the lower critical solution temperature (LCST), the chain of DPDHR-PNIPAM may collapse and change from hydrophilic to hydrophobic to form aggregates and was easy to separate from water to perform recyclable. As a result, it will be a potential fluorescent sensor in the field of tracking Fe3+ in biological processes and environmental monitoring. Meanwhile, the method reported here could provide a method to develop highly effective homogeneous soluble and heterogeneous recoverable fluorescence sensor.

Telechelic biocidal poly(2-oxazoline)s and polycations

Antimicrobial polymers are an important alternative to low molecular weight antibiotics and biocides. While most of such polymers are controlled in their activity by the nature of the backbone, telechelic biocidal polymers are controlled by their end groups. Here, polymers - mostly poly(2-alkyl-2-oxazoline)s - with a biocidal quaternary ammonium end group are discussed regarding their activity, the satellite group effect, and their application in contact-active antimicrobial surfaces and materials. Also the control of other end group functions, such as antibiotics and the end group effects on polycations are discussed.

Grafting‐from Afforded Cyclic Graft Copolymers from Cyclic Anionic Macroinitiator via Lithiation of Tolyl Groups

AbstractCyclic graft copolymers consisting of poly(p‐methylstyrene) backbone and polystyrene branches with relatively low molecular weight distribution are synthesized with grafting‐from approach by living anionic polymerization of styrene from lithiated cyclic poly(p‐methylstyrene)s as multifunctional anionic macroinitiators for vinyl polymerizations. Precursors of the macroinitiators are prepared by ring‐closing metathesis reaction of α,ω‐divinyl‐terminated telechelic polymers. Subsequently, selective lithiation of tolyl groups in the cyclic polymers is conducted by s‐BuLi in the presence of tetramethylethylenediamine in cyclohexane in order to prepare the macroinitiators. Addition of styrene monomer into the cyclic macroinitiators provides shift in SEC to higher molecular weight due to graft polymerization from the macroinitiators to form cyclic graft copolymers. The unique polymer architecture of the obtained cyclic graft copolymers is confirmed by unimolecular observation by using atomic force microscopy.

Modeling Intercolloidal Interactions Induced by Adsorption of Mobile Telechelic Polymers onto Particle Surfaces

We combine the self-consistent field theory and the Derjaguin approximation to predict the polymer-induced colloidal interactions and the nonuniform distributions of the loops and bridges of telech...

Recyclable polymer networks containing hydroxyurethane dynamic cross-links: Tuning morphology, cross-link density, and associated properties with chain extenders

Conventional polymer networks are incapable of being reprocessed or recycled in the melt state, leading to sustainability and economic losses associated with spent polymer networks. With the incorporation of hydroxyurethane dynamic cross-links resulting from reaction of tricyclocarbonate and telechelic amine-terminated polymer, polybutadiene (PB) networks and poly(tetramethylene oxide) (PTMO) networks are reprocessable with full property recovery after multiple molding steps. Two types of small-molecule chain extender are incorporated into these networks to tune their morphologies, cross-link densities and associated properties. Addition of m-xylylenediamine (XYL) chain extender to PTMO networks increases the hard-segment content and leads to nanophase separation, which is absent when XYL is not present, and the elimination of cold crystallization behavior that is observed in PTMO networks without XYL. Addition of XYL also increases the cross-link density and rubbery plateau modulus of both PB and PTMO networks, and the resulting materials remain fully reprocessable. In contrast, addition of divinylbenzene dicyclocarbonate (DVBDC) chain extender enhances the cold crystallization behavior of molded PTMO-based networks and their crystallinity. Addition of DVBDC reduces the cross-link density and rubbery plateau modulus of both PB and PTMO networks, and the resulting networks exhibit selective property losses after reprocessing. This study demonstrates the simple and effective use of chain extenders in achieving tunability of dynamic network properties to satisfy requirements in different potential applications. It also provides a better understanding of structure-property relationships in dynamic covalent networks from both chemical and physical standpoints.

Self-Organization and Flow of Low-Functionality Telechelic Star Polymers with Varying Attraction.

We combine state-of-the art synthesis, simulations, and physical experiments to explore the tunable, responsive character of telechelic star polymers as models for soft patchy particles. We focus on the simplest possible system: a star comprising three asymmetric block copolymer arms with solvophilic inner and solvophobic outer blocks. Our dilute solution studies reveal the onset of a second slow mode in the intermediate scattering functions as the temperature decreases below the θ-point of the outer block, as well as the size reduction of single stars upon further decreasing temperature. Clusters comprising multiple stars are formed and their average dimensions, akin to the single star size, counterintuitively decrease upon cooling. A similar phenomenology is observed in simulations upon increasing attraction between the outer blocks and is rationalized as a result of the interplay between interstar associations and steric repulsion between the star cores. Since our simulations are able to describe the experimental findings reliably, we can use them with confidence to make predictions at conditions and flow regimes that are inaccessible experimentally. Specifically, we employ simulations to investigate flow properties of the system at high shear rates, revealing shear thinning behavior caused by the breakup of interstar associations under flow. On the other hand, the zero-shear viscosity obtained experimentally exhibits a rather weak activation energy, which increases upon rising star concentration. These findings demonstrate the unusual properties of telechelic star polymers even in the dilute regime. They also offer a powerful toolbox for designing soft patchy particles and exploring their unprecedented responsive properties further on.

Near‐Infrared Photoinduced Copper‐Catalyzed Azide‐Alkyne Click Chemistry with a Cyanine Comprising a Barbiturate Group

AbstractA new near‐infrared (NIR) photosensitization system for the activation of a copper‐catalyzed azide‐alkyne cycloaddition click reaction (CuAAC) is reported. Selected cyanines comprising either a cationic or zwitterionic structural pattern were tested for their photosensitization activity to generate Cu(I) by photoreduction of Cu(II) to trigger CuAAC under NIR light at ambient temperature. The photosensitization system described also facilitates chemical modification of UV‐sensitive materials by CuAAC. Upon exposure to light of wavelength 790 nm under anaerobic conditions, the cyanine with a zwitterionic structure comprising a barbiturate group; that is 5‐(6‐(2‐(3‐ethyl‐1,1‐dimethyl‐1H‐benzo[e]indol‐2(3H)‐ylidene)ethylidene)‐2‐(2‐(3‐ethyl‐1,1‐dimethyl‐1H‐benzo[e]‐indol‐3‐ium‐2‐yl)vinyl)cyclohex‐1‐en‐1‐yl)‐1,3‐dimethyl‐2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidin‐4‐olate in combination with Cu(II)‐N,N,N′,N′′,N′′‐pentamethyldiethylene‐triamine complex, exhibited excellent activity with high yields. The possibility to synthesise different macromolecular structures such as telechelic polymers and block copolymers by NIR‐sensitized CuAAC is demonstrated. The structural and molecular characteristics of the intermediates and final products were evaluated by spectral and chromatographic analyses. This new photochemical reaction opens up new pathways for the macromolecular synthesis of complex macromolecular structures and applications requiring light as an activation tool.

Dynamics of Telechelic Ionomers with Distribution of Number of Ionic Stickers at Chain Ends

A new type of ionic telechelic polymer, characterized by a distribution of the number x of ionic groups (sulfonated styrene neutralized by sodium) at the chain ends, was synthesized by a two-step r...

Linear Alternating Associative Polymer with Ultrahigh Molecular Weight: Facile Preparation by Self-Assembly Assisted Dimerization of Anthracene and Rheology in Aqueous Solution.

Alternating associative polymers (AAPs) containing more than two species of alternating hydrophobic and hydrophilic units can form unique physical network and perform interesting rheological behavior in aqueous solution. In this work, an AAP was prepared through self-assembly assisted dimerization of an anthracene-functionalized telechelic associative polymer (AnTAP) in aqueous solution by light irradiation. It is demonstrated that AnTAP can in situ chain extend to AAP with well-defined linear structure and ultrahigh molecular weight through dimerization reaction of anthracene moieties in the core of micelle under light irradiation. Meanwhile, the solution changes from viscoelastic liquid to a free-standing gel, because a physical network that cannot relax in a finite time window has developed along with the dimerization process. The results are therefore of interest not only for understanding the network structure and rheological properties of AAP solution, but also for preparing AAPs with ultrahigh molecular weight by self-assembly assisted photodimerization reactions.