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Title: Effects of Grafting Density on Block Polymer Self-Assembly: From Linear to Bottlebrush

Journal Article · · ACS Nano

Grafting density is an important structural parameter that imparts significant influences over the physical properties of architecturally complex polymers. In this paper, the physical consequences of varying the grafting density (z) were studied in the context of block polymer self-assembly. Well-defined block polymers spanning the linear, comb, and bottlebrush regimes (0 ≤ z ≤ 1) were prepared via grafting-through ring-opening-metathesis polymerization (ROMP). ω-norbornenyl poly(D,L-lactide) (PLA) and polystyrene (PS) macromonomers were copolymerized with discrete co-monomers in different feed ratios, enabling precise control over the grafting density. Small-angle X-ray scattering (SAXS) experiments demonstrate that these graft block polymers can self-assemble into long-range-ordered lamellar structures. For seventeen series of block polymers with variable z, the scaling of the lamellar period with the total backbone degree of polymerization (d* ~ Nbbα) was studied. The scaling exponent α monotonically decreases with decreasing z and exhibits an apparent transition at z ≈ 0.2, suggesting significant changes in the chain conformations. Comparison of two block polymer systems, one that is strongly segregated for all z (System I) and one that experiences weak segregation at low z (System II), indicates that the observed trends are primarily caused by the polymer architectures, instead of segregation strengths. A model is pro-posed in which the characteristic ratio (C), a proxy for the backbone stiffness, scales with Nbb as a function of the grafting density: C ~ Nbbf(z). To the best of our knowledge, this report represents the first study of scaling behavior for the self-assembly of block polymers with variable grafting density. Lastly, the relationships disclosed herein provide valuable insights into conformational changes with grafting density, thus introducing new opportunities for future block polymer design.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Grant/Contract Number:
AC02-06CH11357; AR0000683
OSTI ID:
1416003
Journal Information:
ACS Nano, Vol. 11, Issue 11; ISSN 1936-0851
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 74 works
Citation information provided by
Web of Science

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Cited By (10)

Effect of side chain and backbone length on lamellar spacing in polystyrene‐block‐poly(dimethyl siloxane) brush block copolymers journal March 2019
Precise polyethylene derivatives bearing mesogenic side-chains: delicate self-assembly depending on graft density journal January 2020
Synthesis and Applications of Compartmentalised Molecular Polymer Brushes journal May 2018
Theoretical prediction of an isotropic to nematic phase transition in bottlebrush homopolymer melts journal September 2019
Synthese und Anwendung von kompartimentierten molekularen Polymerbürsten journal May 2018
Solution self-assembly of poly(3-hexylthiophene)–poly(lactide) brush copolymers: impact of side chain arrangement journal January 2018
Handwritable one-dimensional photonic crystals prepared from dendronized brush block copolymers journal January 2019
Synthesis and Self‐Assembly of Mixed‐Graft Block Copolymers journal May 2019
Dilute solution structure of bottlebrush polymers journal January 2019
Synthetic Methodologies for Chelating Polymer Ligands: Recent Advances and Future Development journal December 2018

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