Engineering Orthogonality in Supramolecular Polymers: From Simple Scaffolds to Complex Materials

Abstract

Owing to the mastery exhibited by Nature in integrating both covalent and noncovalent interactions in a highly efficient manner, the quest to construct polymeric systems that rival not only the precision and fidelity but also the structure of natural systems has remained a daunting challenge. Supramolecular chemists have long endeavored to control the interplay between covalent and noncovalent bond formation, so as to examine and fully comprehend how function is predicated on self-assembly. The ability to reliably control polymer self-assembly is essential to generate "smart" materials and has the potential to tailor polymer properties (i.e., viscosity, electronic properties) through fine-tuning the noncovalent interactions that comprise the polymer architecture. In this context, supramolecular polymers have a distinct advantage over fully covalent systems in that they are dynamically modular, since noncovalent recognition motifs can be engineered to either impart a desired functionality within the overall architecture or provide a designed bias for the self-assembly process. In this Account, we describe engineering principles being developed and pursued by our group that exploit the orthogonal nature of noncovalent interactions, such as hydrogen bonding, metal coordination, and Coulombic interactions, to direct the self-assembly of functionalized macromolecules, resulting in the formation of supramolecular polymers. To begin, we describe our efforts to fabricate a modular poly(norbornene)-based scaffold via ring-opening metathesis polymerization (ROMP), wherein pendant molecular recognition elements based upon nucleobase-mimicking elements (e.g., thymine, diaminotriazine) or SCS-Pd(II) pincer were integrated within covalent monofunctional or symmetrically functionalized polymers. The simple polymer backbones exhibited reliable self-assembly with complementary polymers or small molecules. Within these systems, we applied successful protecting group strategies and template polymerizations to enhance the control afforded by ROMP. Main-chain-functionalized alternating block polymers based upon SCS-Pd(II) pincer-pyridine motifs were achieved through the combined exploitation of bimetallic initiators and supramolecularly functionalized terminators. Our initial design principles led to the successful fabrication of both main-chain- and side-chain-functionalized poly(norbornenes) via ROMP. Utilizing all of these techniques in concert led to engineering orthogonality while achieving complexity through the installation of multiple supramolecular motifs within the side chain, main chain, or both in our polymer systems. The exploitation and modification of design principles based upon functional ROMP initiators and terminators has resulted in the first synthesis of main-chain heterotelechelic polymers that self-assemble into A/B/C supramolecular triblock polymers composed of orthogonal cyanuric acid-Hamilton wedge and SCS-Pd(II) pincer-pyridine motifs. Furthermore, supramolecular A/B/A triblock copolymers were realized thro...

Modular and orthogonal synthesis of hybrid polymers and networks

“…An attractive approach is the combination of orthogonal chemistry with orthogonal supramolecular assembly. 218 …”

Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]-Modified Patchy Particles

“…demonstrated that, unlike DPV 2+ which forms the species is comparable to that measured for PMV •+ ⊂CB[7] (phenylmethylviologen, log K PMV•+⊂CB[7] = 4.60 ± 0.07) or BMV •+ ⊂CB[7] (BMV = benzyl-methyl viologen,27 log K BMV•+⊂CB[7] = 4.9 ± 0.1) which suggests that these three radical host-guest complexes have similar binding modes. DPV •+ ⊂CB…”

“…The emulsion polymerization was initiated using potassium persulfate, effectively installing the sulfonated moieties on the initial clusters 27 and, thus, being exposed on the patches after encapsulation. The encapsulation polymerization was initiated by benzoyl peroxide, resulting in an unmodified 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 poly(styrene) shell surface.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…(10) preparation of stereoregular polymers via ROMP [37]; (11) preparation of self-assembled supramolecular polymers [38]; (12) combining ROMP and thiol-ene coupling chemistry for preparation of linear and nonlinear macromolecules [39]; (13) synthesis of cyclo-polyolefins through ring expanding metathesis polymerization [40]; (14) precision polymers through ADMET polymerization [41,42]; (15) systematic studies of morphological changes of ADMET-derived precision polyethylene [43]; (16) concurrent cross metathesis and enzymatic oxidation reactions [44]; (17) rhenium oxide based olefin metathesis [45]; and (18) olefin metathesis over molybdenum-exchanged zeolites [46]. Additional reviews in languages other than English include: (1) olefin metathesis in complex synthesis [47]; (2) Z-selective olefin metathesis catalysts and their applications [48]; (3) modification of biodiesel using olefin metathesis [49]; (4) cyclic aminocarbene complexes (Bertrand carbene complexes) in olefin metathesis reactions [50]: (5) progress in ROMP of dicyclopentadiene [51]; and (6) the role MgO in WO 3 / SiO 2 catalyzed olefin metathesis [52].…”