Precision Polyolefins

Berda, Erik B.; Wagener, Kenneth B.

doi:10.1002/9780470825150.ch10

Cited by 3 publications

(3 citation statements)

References 73 publications

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“…A variety of folded polymers were established including tadpole (P-shaped), pseudocyclic (Q-shaped), bicyclic (8-shaped), and knotted (α-shaped) macromolecular origamis. Well-defined chain-growth methods and step-growth chemistries such as ADMET and the use of multicomponent reactions are potentially advantageous for the fabrication of advanced SCNP architectures.…”

Section: The Pressing Challengesmentioning

confidence: 99%

What Is Next in Single-Chain Nanoparticles?

2015

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With the increasing appeal of nanotechnology, there is a demand for development of synthetic techniques for the fabrication of nanosized objects that allow for precise size control and tailored functionalization. To this end, the collapse or folding of single polymer chains into architecturally defined nanostructures is a rapidly growing research topic in polymer science. Many synthetic approaches have been developed for the formation of single-chain nanoparticles (SCNP), and a variety of characterization methods and computational efforts have been utilized to detail their formation and probe their morphological characteristics. Interest in this field continues to grow partially due to the variety of potential applications of SCNP including catalysis, sensors, nanoreactors, and nanomedicine. While numerous developments have been made, the field is continuing to evolve, and there are still many unanswered questions regarding synthesis and characterization of SCNP. This Perspective serves to identify recent accomplishments in the synthesis and characterization of SCNP while distinguishing areas that are in need of advancement and innovation to move forward. This includes exploring more complex synthetic strategies, obtaining folding control, employing nanoparticle functionalization, developing scalable methods, investigating hierarchical self-assembly of SCNP, and exploiting unique characterization techniques and in-depth simulations.

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Section: The Pressing Challengesmentioning

confidence: 99%

What Is Next in Single-Chain Nanoparticles?

2015

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“…1 Many of these precision polyethylenes were synthesized via acyclic diene metathesis polymerization followed by hydrogenation. 2 A second common route is controlled ring-opening metathesis polymerization that also provides precision polyethylene-like systems when the specific site for ring opening and regularity of the monomer addition can be maintained during polymerization. 3−5 Long-spaced polyacetals and polycarbonates have been synthesized via classical polycondensation of the corresponding α, ω-diols, and diethoxymethane or dimethylcarbonate at high temperature under vacuum.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The series of recently synthesized long-spaced polyacetals, also termed long-spaced polyformals, belongs to the extensive families of precision polyethylenes with molecular structures characterized by a linear polyethylene backbone decorated at precise equal distances by in-chain or side-chain (pendant) functional groups . Many of these precision polyethylenes were synthesized via acyclic diene metathesis polymerization followed by hydrogenation . A second common route is controlled ring-opening metathesis polymerization that also provides precision polyethylene-like systems when the specific site for ring opening and regularity of the monomer addition can be maintained during polymerization. − …”

Section: Introductionmentioning

confidence: 99%

Crystallization of Long-Spaced Precision Polyacetals I: Melting and Recrystallization of Rapidly Formed Crystallites

et al. 2019

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Rapidly melt-crystallized polyethylenes with acetal groups (−O–CH2–O−) precisely spaced by 12, 18, 19, or 23 methylene backbone carbons exhibit two reorganizations and three melting endotherms on heating at relatively low heating rates. Real-time wide-angle X-ray diffraction (WAXD) experiments further confirm that these transitions are associated with a reorganization to a different crystalline structure. The differential scanning calorimetry endotherms are associated with melting of the initially formed disordered (or hexagonal) phases, followed by melting of Form I and by melting of Form II crystals with increasing temperature. In parallel with these structural changes, the long spacing undergoes a discrete step increase at the polymorphic transitions. Upon the transition from disordered to Form I crystals, the core crystal thickness increases by one repeating unit, whereas the crystal thickness remains basically unchanged during the transition from Form I to Form II crystallites. The effect of even vs odd CH2 spacer on the observed melting temperatures is prevalent for spacer <10 CH2 units. The even or odd number of methylenes between acetals also affects the type and kinetics of packing assembly in layered crystallites. Although a disordered mesomorphic-like structure develops under fast cooling in odd-spaced polyacetals (PA-19, PA-23), the formation of Form I crystals cannot be bypassed in PA-12 and PA-18. Furthermore, some differences are also found in the WAXD patterns of Form II between odd- and even-spaced polyacetals, denoting that staggering of the acetals in the crystallites is affected by the configuration of consecutive acetals with respect to the methylene sequence.

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