Synthesis and Characterization of Spirocyclic Mid-Block Containing Triblock Copolymer

Polymers containing cyclic derivatives are a new class of macromolecular topologies with unique properties. Herein, we report the synthesis of a triblock copolymer containing a spirocyclic mid-block. To achieve this, a spirocyclic polystyrene (cPS) mid-block was first synthesized by atom transfer radical polymerization (ATRP) using a tetra-functional initiator, followed by end-group azidation and a copper (I)-catalyzed azide-alkyne cycloaddition reaction. The resulting functional cPS was purified using liquid chromatography techniques. Following the esterification of cPS, a macro-ATRP initiator was obtained and used to synthesize a poly (methyl methacrylate)-block-cPS-block-poly (methyl methacrylate) (PMMA-b-cPS-b-PMMA) triblock copolymer. This work provides a synthetic strategy for the preparation of a spirocyclic macroinitiator for the ATRP technique and as well as liquid chromatographic techniques for the purification of (spiro) cyclic polymers.

PolyDODT: a macrocyclic elastomer with unusual properties

Reversible Radical Recombination Polymerization (R3P) using triethylamine (TEA), H2O2 and air is a scalable and green method for the synthesis of biodegradable polysulfides.

One-Pot Synthesis of Alternating (Ultra-High Molecular Weight) Multiblock Copolymers via a Combination of Anionic Polymerization and Polycondensation

This article presents a fast, straightforward synthesis approach to polymerize alternating multiblock copolymers, ultra-high molecular weight (UHMW) (homo)polymers as well as precursors for complex macromolecular topologies such as comb or barbwire architectures. The one-pot synthesis strategy proposed in this work is based on anionic polymerization via a bifunctional initiator and the subsequent linking of macro dianions with a bifunctional linker, additionally overcoming the limitations associated with the monomer reactivity. Thus, the synthetic route guarantees the repeating size of polymer blocks and an equal distribution of functional groups in precursors for complex topologies. Dianions of polystyrene (PS), polyisoprene-b-polystyrene-b-polyisoprene, and poly-2-vinylpyridine-b-polystyrene-b-poly-2-vinylpyridine are linked with α , α ' -dibromo-para-xylene to UHMW and multiblock copolymers. Multiblock copolymers with on average up to 50 well-defined alternating A and B blocks are accessible within 15 min.

Analysis of cyclic polymer purity by size exclusion chromatography: a model system

Because cyclic polymers have intriguing physical properties, considerable synthetic strategies have been developed to create a wide variety of cyclic architectures.

Chain-Conformation-Directed Polymerization Cyclization for Effective Synthesis of Macrocycles in Bulk

Biological cyclization is highly efficient, and this can be attributed to the conformation of the backbone of the biopolymer. Taking advantage of metal-coordination geometry, we developed a method for conformation-directed polymerization cyclization through rational design of metal carbonyl monomers that could be used to produce cyclic macromolecules, even in bulk. ^P FpR [^P Fp=(PPh₂ (CH₂ )₃ Cp)Fe(CO)₂ with the phosphine group tethered on the cyclopentadiene (Cp) ring; R=CH₃ or (CH₂ )₅ CH₃ ] was designed and synthesized for migration insertion polymerization to generate P(^P FpR) with the polymer backbone containing Cp-Fe bonds. Growth of the backbone led to a cyclic conformation with close end-to-end distances, which facilitated the cyclization. This conformation-directed cyclization was attributed to the piano-stool metal-coordination geometry of the repeating units and the low rotational barrier of the Cp-Fe bonds in the backbone. The produced macrocycles, which contain a metal carbonyl coordination structure in their backbones, are rigid, unlike many organic macrocycles. The macrocycles thus have a large excluded volume. This new type of metal carbonyl macrocycle will be of interest as a building block for supramolecular chemistry and in the exploration of novel materials.

Synthesis of a cyclic-brush polymer with a high grafting density using activated ester chemistry via the “grafting onto” approach

A concept for preparing cyclic-brush polymers with high grafting densities combining a ring-closure strategy and activated ester chemistry as a post-modification method via the grafting onto approach.

Scaling behavior of knotted random polygons and self-avoiding polygons: Topological swelling with enhanced exponent

We show that the average size of self-avoiding polygons (SAPs) with a fixed knot is much larger than that of no topological constraint if the excluded volume is small and the number of segments is large. We call it topological swelling. We argue an "enhancement" of the scaling exponent for random polygons with a fixed knot. We study them systematically through SAP consisting of hard cylindrical segments with various different values of the radius of segments. Here we mean by the average size the mean-square radius of gyration. Furthermore, we show numerically that the topological balance length of a composite knot is given by the sum of those of all constituent prime knots. Here we define the topological balance length of a knot by such a number of segments that topological entropic repulsions are balanced with the knot complexity in the average size. The additivity suggests the local knot picture.

Knotting probability of self-avoiding polygons under a topological constraint

We define the knotting probability of a knot K by the probability for a random polygon or self-avoiding polygon (SAP) of N segments having the knot type K. We show fundamental and generic properties of the knotting probability particularly its dependence on the excluded volume. We investigate them for the SAP consisting of hard cylindrical segments of unit length and radius r_ex. For various prime and composite knots, we numerically show that a compact formula describes the knotting probabilities for the cylindrical SAP as a function of segment number N and radius r_ex. It connects the small-N to the large-N behavior and even to lattice knots in the case of large values of radius. As the excluded volume increases, the maximum of the knotting probability decreases for prime knots except for the trefoil knot. If it is large, the trefoil knot and its descendants are dominant among the nontrivial knots in the SAP. From the factorization property of the knotting probability, we derive a sum rule among the estimates of a fitting parameter for all prime knots, which suggests the local knot picture and the dominance of the trefoil knot in the case of large excluded volumes. Here we remark that the cylindrical SAP gives a model of circular DNA which is negatively charged and semiflexible, where radius r_ex corresponds to the screening length.

Statistical and Dynamical Properties of Topological Polymers with Graphs and Ring Polymers with Knots

We review recent theoretical studies on the statistical and dynamical properties of polymers with nontrivial structures in chemical connectivity and those of polymers with a nontrivial topology, such as knotted ring polymers in solution. We call polymers with nontrivial structures in chemical connectivity expressed by graphs "topological polymers". Graphs with no loop have only trivial topology, while graphs with loops such as multiple-rings may have nontrivial topology of spatial graphs as embeddings in three dimensions, e.g., knots or links in some loops. We thus call also such polymers with nontrivial topology "topological polymers", for simplicity. For various polymers with different structures in chemical connectivity, we numerically evaluate the mean-square radius of gyration and the hydrodynamic radius systematically through simulation. We evaluate the ratio of the gyration radius to the hydrodynamic radius, which we expect to be universal from the viewpoint of the renormalization group. Furthermore, we show that the short-distance intrachain correlation is much enhanced for real topological polymers (the Kremer⁻Grest model) expressed with complex graphs. We then address topological properties of ring polymers in solution. We define the knotting probability of a knot K by the probability that a given random polygon or self-avoiding polygon of N vertices has the knot K. We show a formula for expressing it as a function of the number of segments N, which gives good fitted curves to the data of the knotting probability versus N. We show numerically that the average size of self-avoiding polygons with a fixed knot can be much larger than that of no topological constraint if the excluded volume is small. We call it "topological swelling".

Viscosity of ring polymer melts

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as function of the number of entanglements Z. In the unentangled regime η0,linear/η0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/η0,ring=2. In the entanglement regime, the Z-dependence of rings viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 Collapse

Key Words

• entanglements
• molecular weight
• purification
• ring polymers
• viscosity

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MESH Headings Collapse

Grants

• P01 HL108808 NHLBI NIH HHS
• P50 HL107168 NHLBI NIH HHS

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Affiliation(s)

Rossana Pasquino FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece
Thodoris C Vasilakopoulos University of Athens, Department of Chemistry, Athens 15771, Greece
Youn Cheol Jeong Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Hyojoon Lee Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Simon Rogers FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece
George Sakellariou University of Athens, Department of Chemistry, Athens 15771, Greece
Jürgen Allgaier Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Atsushi Takano Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
Ana R Brás Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Taihyun Chang Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Sebastian Gooßen Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Wim Pyckhout-Hintzen Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Andreas Wischnewski Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Nikos Hadjichristidis University of Athens, Department of Chemistry, Athens 15771, Greece ; King Abdullah University of Science and Technology, Division of Physical Sciences & Engineering, KAUST Catalysis Center, Polymer Synthesis Laboratory, Thuwal, Kingdom of Saudi Arabia
Dieter Richter Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Michael Rubinstein Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
Dimitris Vlassopoulos FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece ; University of Crete, Department of Materials Science & Technology, Heraklion 71003, Greece

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Universality in the diffusion of knots

We have evaluated a universal ratio between diffusion constants of the ring polymer with a given knot K and a linear polymer with the same molecular weight in solution through the Brownian dynamics under hydrodynamic interaction. The ratio is found to be constant with respect to the number of monomers, N , and hence the estimate at some N should be valid practically over a wide range of N for various polymer models. Interestingly, the ratio is determined by the average crossing number (N{AC}) of an ideal conformation of knotted curve K , i.e., that of the ideal knot. The N{AC} of ideal knots should therefore be fundamental in the dynamics of knots.