1. Virginia Tech
Department of Chemistry
RESEARCH
John B. Matson
jbmatson@vt.edu
(540) 231-3329
PHOTO OF
RESEARCH PI
Bottlebrush Synthesis: Grafting-From vs. Transfer-To
Karen N. Tran, Scott C. Radzinski, Jeffrey C. Foster, Samantha J. Scannelli, John B. Matson
Department of Chemistry and Macromolecules and Interface Institute, Virginia Tech
Introduction
Bottlebrush polymers are becoming much more relevant to the
polymer industry due to their structures, shape persistence,
nanoscopic dimensions, and unique mechanical and rheological
properties. They differ from linear polymers in a sense that they
do not interact via chain entanglements, rather they are
encompassed with polymeric side-chains grafted to a polymer
backbone. Because of the grafting density and steric repulsion
between polymeric neighbors, the backbone is able to adopt a
chain-extended conformation. The size and shape of bottlebrush
polymers also allows for the in vivo delivery of therapeutic
agents.
Synthesis of Bottlebrush Polymers
Bottlebrush polymers can be prepared in one of four approaches:
the grafting-from strategy, the grafting-to methodology, the
grafting-through or macromonomer (MM) approach, or the
transfer-to approach. The grafting-from strategy is used to
synthesize bottlebrush polymers with relatively higher molecular
weights. It involves an attachment of an initiator to a polymer
chain and grows from the initiator groups.
Transfer-To Polymerization
The transfer-to approach is a mix of the grafting-from and grafting-to;
polymeric radicals will detach from the bottlebrush backbone and
propagate freely in solution while eventually returning to the
backbone through a chain-transfer reaction with a pendant chain-
transfer agent (CTA). The transfer-to approach is used for bottlebrush
polymers with lower dispersities and higher possible conversions
compared to usual RAFT grafting-from methods.
References
[1] S. C. Radzinski, J. C. Foster and J. B. Matson, Polymer Chemistry 2015,
6, 5643-5652.
[2] S. Banerjee, T. K. Paira and T. K. Mandal, Polymer Chemistry 2014, 5,
4153-4167.
RAFT Polymerization
Reversible addition-fragmentation chain transfer is a form of radical
polymerization. It involves a substituted monomer in the presence of a
suitable chain transfer agent (CTA). Common agents include
thiocarbonylthio compounds. The R and Z substituents impact the
reaction kinetics and the degree of structural control. 12 14 16 18
Retention Time (min)
Conclusion
The backbone of the bottlebrush has been synthesized and the
comparison between the two methods is currently under
investigation.
Figure 1. Bottlebrush Polymerization
Figure 2. Grafting-From Polymerization
Figure 3. Transfer-To Polymerization
CTA pCTA Bottlebrush Polymer
15 17 19
Retention Time (min)
The backbone was synthesized using ring-opening metathesis
polymerization (ROMP)
The CTA was tested under normal RAFT conditions to confirm its
reactivity with styrene
Time(h) Mn Đ
1 700 1.07
2 1100 1.07
4 1500 1.17
6 1800 1.14
10 2300 1.13
24 4000 1.13
Synthesis of Chain Transfer Agent (CTA)
The CTA was designed for transfer-to polymerization.