Topology-Reset Execution: Repeatable Postcyclization Recyclization of Cyclic Polymers

Article abstract of DOI:10.1002/anie.201809621

Repeatable topological transformation of polymers for the modulation of material functions is a challenge. We have developed a method for repeatedly resetting a cyclic macromolecular architecture to a linear architecture by photostimulation, namely, topol

Full text of DOI:10.1002/anie.201809621

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Accepted Article
Title: Topology-Reset Execution: Repeatable Post-Cyclization Re-
cyclization of Cyclic Polymers
Authors: Satoshi Honda, Minami Oka, Hideaki Takagi, and Taro Toyota
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201809621
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10.1002/anie.201809621
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Topology-Reset Execution: Repeatable Post-Cyclization Re-
cyclization of Cyclic Polymers
Satoshi Honda*, Minami Oka, Hideaki Takagi, and Taro Toyota
Abstract: Repeatable topological transformation of polymers has
been a challenge for realizing modulation of material functions. Here
we developed a methodology for repeatedly resetting a cyclic
macromolecular architecture to a linear one by photostimulation,
namely, topology-reset execution (T-rex) based on photochemistry of
recently achieved solvent-free repeatable transformation between
network and star MAs with poly(n-butyl acrylate) oligomer and
poly(dimethylsiloxane) (PDMS).[4] The chemistry of network
scission and reformation relies on photochemistry of
hexaarylbiimidazole (HABI), which can be synthesized by
hexaarylbiimidazoles
(HABI).
We
synthesized
cyclic
oxidizing
2,4,5-triphenylimidazole
(lophine)
into
poly(dimethylsiloxane)s (PDMSs) containing various ring sizes in-
chain linked with HABI. UV irradiation to the cyclic PDMSs produced
telechelic linear PDMSs having triphenylimidazoryl radical (TPIR) end
groups and following termination of UV enabled their end-to-end re-
cyclization by the recoupling of TPIRs into HABIs. The cyclic PDMSs
also respond to ultrasound to decrease their molecular weights (MWs)
by site-specific cleavage of in-chain HABIs and we are able to reset
the MWs by following photo-triggered T-rex after all. Furthermore, T-
rex enables solvent-free switching of rheological properties with
retaining liquid character of PDMS. The T-rex approach developed
here is versatile, fast, repeatable, and enables switching of material
functions at a desired timing.
triphenylimidazoryl radical (TPIR) as an activation step and
following spontaneous coupling between the generated TPIRs
(Figure 1a, left). HABI undergoes cleavage of the covalent bond
between the two imidazoles to generate a pair of TPIRs and their
recoupling into HABI again upon ON–OFF of photoirradiation
(Figure 1a, left).[5] This chemistry enables network–star
topological transformation and solvent-free isothermal liquid–
nonliquid conversion of polymeric materials.[4] Hence, it can be
potentially extended to repeatable transformation between
various combinations of topologically unique polymers. Herein,
we report a methodology for repeatedly resetting a cyclic
topological geometry to a telechelic linear one simply by
irradiating UV to in-chain HABI-functionalized cyclic PDMSs
(Figure 1a, right). The methodology, named “topology-reset
execution (T-rex)”, enables post-cyclization re-cyclization (PCR)
of polymer components by following termination of
photoirradiation.
Progress in organic synthesis and precise polymerization
techniques has led to the construction of topologically unique
macromolecular architectures (MAs). Although MAs often
differentiate their properties, it is generally difficult to repeatedly
transform them into other MAs. Accordingly, an ongoing
challenge is to develop a methodology enabling repeated
transformation of MAs and some commendable studies have
appeared.[1] Such strategies can, in principle, be applicable for
repeatable switching of functions with polymeric materials.
Compared to other methodologies, repeated transformation of
MAs should be advantageous for controlling properties of
polymers because it does not require change in chemical
composition and molecular weight (MW), control of
stereoregularity, use of additives, but is applicable irrespective of
the type of polymer backbones. Among various MAs, cyclic
polymers are distinct because of their endless nature.[2]
Particularly, repeatable transformation of linear and cyclic MAs in
solution state has been studied with sophisticated molecular and
reaction designs,[1e, 3] yet development of a facile and versatile
system without using solvent is imperative for extending its
concept to practical applications. On the other hand, we have
Linear PDMSs were synthesized by ring opening
polymerization of hexamethylcyclotrisiloxane initiated from H2O[6]
and vinyl end groups were introduced by terminating with
chlorodimethylvinylsilane (Scheme S1, top). The resulting α,ω-
divinyl PDMS was then reacted with hydrosilane-functionalized
lophine in the presence of Karstedt’s catalyst to afford PDMS
having lophine end groups (L) (Scheme S1, bottom). Similar to
our previous report,[4] the lophine end groups of L were oxidized
to produce telechelic linear PDMS with TPIR end groups (L*),
where the TPIRs readily coupled into HABIs in the reaction
mixture to produce inter- and intra-molecularly reacted PDMS
1
(Cmix) (Figure 1b). Comparison of H NMR spectra revealed the
complete dissapearance of –NH signal at 11.7 ppm (marked e)
visible in the spectrum of L (Figure S1a) after forming HABI
(Figure S1b). Moreover, signals derived from methylene protons
(marked b and c) and those from aromatic region became
complex. This is due to the possible three combinations of
covalent bonds in HABI, i.e., C–N, N–N, and C–C bonds as
reported preivously.[7] SEC of Cmix showed a bimodal trace with a
broad dispersity (Đ), and the trace significantly shifted from the
former (Figure 2a) toward higher MW region (Figure 2b). The
existence of high MW fraction suggested intermolecular reaction
between the generated TPIRs to cause chain extension. On the
other hand, peak MW (Mp) of the second highest peak (Figure 2b)
decreased in comparison with that of the parent L (Figure 2a).
The reduction in Mp, i.e., apparent MW indicates intramolecular
cyclization as observed in various cyclization reactions.[2b]
[*]
Dr. S. Honda, M. Oka, Dr. T. Toyota
Department of Basic Science, Graduate School of Arts and
Sciences, The University of Tokyo
3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan)
E-mail: c-honda@mail.ecc.u-tokyo.ac.jp
Dr. H.Takagi
Photon Factory, Institute of Materials Structure Science, High
Energy Accelerator Research Organization
1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
In the course of our study, we noticed that Cmix was viscous
liquid though L was solid (Figure 1b, right). This difference is
strange on the surface because Cmix has MW larger than L and
chemical compositions are quite similiar. IR spectroscopy verified
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the formation of hydrogen
bonding (H-bonding) between
the lophines within L. Several
types of H-bonding between
imidazoles are possible and
they typically show a broad
stretching vibrational band due
to N–H∙∙∙N at 2500–3500
cm−1.[8] Obviously, IR spectrum
of
L
showed the broad
absorption at the relevant
wavenumber region (Figure
S2a); however, such broad
absorption disappeared after
forming HABI as proved in the
spectrum of Cmix (Figure S2b).
The formation of H-bonding
within
supported
L
has also been
by differential
scanning calorimetry (DSC)
with the endotherm at 82 °C
(1.9 J/g) upon heating (Figure
S3a). This thermal behavior is
in good agreement with that of
poly(propylene oxide) having
H-bonding
end
groups
reported in the literature.[9]
From the DSC of Cmix (Figure
S3b), it is also apparent that
the disappearance of the
Figure 1. (a) Conceptual illustration of T-rex and PCR based on photochemistry of HABI. (b) Synthesis of in-chain
HABI-functionalized Cmix from L and their appearances (right).
corresponding
again demonstrating complete
endotherm,
production of TPIRs and their recoupling into HABIs occur at bulk
and in solution.[4] In the present case, while L* showed TPIR-
derived strong absorbance in the range 450–650 nm with the
peak at 568 nm (A568) in its UV-vis spectrum, the absorbance
completely disappeared from that of Cmix (Figure S5). It is
remarkable that complete disappearance of absorption indicates
no unreacted L* or longer linear PDMS having TPIR end groups
exists in Cmix. From time-course plots of A568 for products after UV
irradiation to THF solutions of Cmix (1.0 and 0.1 mg/mL) recorded
immediately after terminating UV irradiation (Figure S6), it is
disclosed that almost all of TPIRs reverted into HABI within 30
min. Next, SEC of the products after UV irradiation to THF
solutions of Cmix (10, 5.0, 1.0, and 0.5 mg/mL) showed decrease
of the trace at higher MW region with lowering concentration
(Figure 2c–g). The higher MW fraction eventually disappeared at
the concentration of 0.10 mg/mL and the Mp of the resulting
unimodal trace was 3600 (Figure 2g). The Mp ratio compared to
conversion of lophines into HABIs. Analogous to thermoplastic
elastomers formed by triblock copolymers, linear polymers having
H-bonding groups at both chain ends can cause microphase
separation.[10] As was studied in detail, such materials show
characteristic patterns in their small-angle x-ray scattering
(SAXS) profiles and the profiles can be fitted with Percus–Yevick
(PY) model, assuming random placement of aggregates of end
groups immiscible to main chain.[11] Indeed, the SAXS profile of L
showed a scattering pattern similar to those reported in the above
studies (Figure S4a, red line).[11] The peak scattering vector (q*)
was 1.01, corresponding to an averaged distance (d = 2π/q*) of
6.2 nm between two aggregates. The intensity plots were well-
fitted with a curve determined by PY model (Figure S4b) and
radius of an aggregate of end groups (R) was calculated as 2.5
nm; the d and R well represented the network structure as
illustrated (Figure S4c). On the other hand, only a slight broad
scattering assignable to correlation hole[12] appeared in the SAXS
of Cmix (Figure S4a, blue line). Taken together, disappearance of
H-bonding by forming HABI evidently avoided formation of
aggregates and led Cmix homogeneous liquid.
The synthesized Cmix provides three intriguing features. The
first feature is photo-triggered cleavage and reformation of the
HABIs embedded in the PDMS backbone. Screening an
optimized condition for end-to-end cyclization reaction is
generally cumbersome and wasteful. If polymer materials
containing various ring sizes produced in the screening process
undergo re-cyclization, they do not become wastes. Thus, we
initiated a rigorous study of UV irradiation experiments. As was
previously validated with ESR and UV–vis spectral studies,
that of L was 0.84 (3600/4300), which is similar to the reported
2b]
values,[1c,
suggesting production of unimolecularly cyclized
PDMS (Cuni). The MALDI-TOF mass spectra of L (Figure S7a)
and Cuni (Figure S7b) showed a series of peaks with an interval
of 74 mass units corresponding to the repeating dimethyl siloxane
unit. Moreover, each peak exactly matched the total molar mass
of the expected chemical structure of L and Cuni. For the former,
the peak at the m/z = 2747.85, which is assumed to the adduct
with H+, corresponds to L possessing the expected chemical
structure with a DPn of 25; (C2H6OSi) × 25 + C54H62 N4OSi4 plus
H+ equals 2747.88. And for the latter, the peak at the m/z =
2746.22, which is assumed to the adduct with H+, corresponds to
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Figure 2. SEC traces of (a) L, (b) Cmix, and products after UV irradiation to THF solution of Cmix at the concentrations of (c) 10.0 mg/mL, (d) 5.0 mg/mL, (e)
1.0 mg/mL, (f) 0.5 mg/mL, and (g) 0.1 mg/mL, respectively, determined using UV detector. The elution time corresponding to the Mp of L was indicated with
the dashed line. SEC traces of (h) a mixture of the products after UV irradiation to THF solutions of Cmix at the concentrations of 10.0, 5.0, 1.0, and 0.5 mg/mL,
(i) its UV irradiated product (the concentration of the reaction THF solution was 0.1 mg/mL), and (j) the product after further UV irradiation at bulk.
Cuni possessing the expected chemical structure with a DPn of 25;
(C2H6OSi) × 25 + C54H60 N4OSi4 plus H+ equals 2745.87. The
molar masses of L and Cuni differ by 2 mass units, confirming the
elimination of two hydrogen atoms through the activation step
(Figure 1a). Hence, unimolecularly cyclized Cuni was undoubtedly
produced under dilution (Figure 3). We then mixed the remained
UV irradiated products (products corresponding to Figure 2c, d, e,
and f) and subjected to SEC analysis. Of course, the SEC trace
of the mixed product showed the trace (Figure 2h) similar to that
of the parent Cmix (Figure 2b). Upon T-rex to its THF solution at
the concentration of 0.10 mg/mL, the resulting product showed
the SEC trace (Figure. 2i) surprisingly similar to that of Cuni (Figure
2g), revealing repeatable nature of T-rex and following PCR
process. Moreover, further T-rex for the product without solvent
for only 1 min resulted in increase of MW (Figure 2j),
demonstrating chain extension under the solvent-free condition
(Figure 3). Importantly, all of the above experiments of T-rex were
achieved in air by taking advantage of the stability of TPIR against
oxygen.[13]
In the second, Cmix displays response to a mechanical
stimulus. Among a wide variety of mechanical responses of
polymer materials,[14] main-chain scission is crucial because it
seriously impairs their performance. Ultrasound is often utilized
for causing main chain scission and for triggering reaction with
⋅⋅⋅
Cmix
no UV
UV
solvent-free condition
Ph
Ph
N
N
N
Ph
Ph
N
N
Si
Si
Si
Si
O n
compounds
responding
to
mechanical
stimuli
Si
Ph
O
O
Si
n
N
(mechanophores).[15] We envisioned that in-chain HABIs in cyclic
PDMSs will be sacrificially cleaved into TPIRs upon ultrasound
irradiation but will reproduce again. Interestingly, SEC traces of
products immediately after ultrasound irradiation to Cmix displayed
two distinct changes in their MW: (i) increase of MW in the initial
stage (~10 min); and (ii) subsequent gradual decrease into a
converged MW (10~120 min). Compared to the SEC curve of Cmix
(Figure 4a), initial increase of MW is apparent by the shift of Mp
toward higher MW region (Figure 4b). About 120% increase of Mp
corresponds to the apparent MW ratio between cyclic and linear
polymers with the identical absolute MW, suggesting cyclic to
linear transformation took place by main chain scission. On the
other hand, the latter stage supports further main chain scission
(Figure 4c). As was established by conventional studies,
N
Ph
N
Ph
Ph
L*
no UV
diluted condition
UV
Si
Si
Si
Si
O n
Si
O
O
Si
n
N
N
N
N
Ph
Ph
Ph
Ph
Cuni
Figure 3. Synthesis of unimolecularly cyclized PDMS (Cuni) by photo-
triggered T-rex under dilution
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Figure 4. SEC traces of (a) Cmix, products after ultrasound irradiation for (b) 10 min and (c) 120 min and (d) a product after further UV365 irradiation at the THF
concentration of ca. 0.1 mg/mL. Dashed line indicates Mp of the larger fraction at the ultrasound irradiation time of 10 min. Time-course plots of (e) G’ and G’’
and (f) tan δ upon ON–OFF of UV irradiation to Cmix. The sample was irradiated with UV for 3 min during time ranges colored in pink.
ultrasound irradiation causes main chain scission of polymers, yet
the response is dependent upon MW; as polymers below their
MW thresholds do not respond to ultrasound.[15] Time-course
plots of MW upon ultrasound irradiation indeed resulted in
convergence of MW (Figure S8). On the other hand, the SEC
traces remained almost unchanged upon ultrasound irradiation to
a smaller MW mixture prepared by irradiating UV to THF solution
(1.0 mg/mL) of Cmix (Figure S9). These support the existence of a
MW threshold similar to the conventional study.[15] Finally, the
ultrasound-irradiated product containing high MW fraction (Figure
4c) was subjected to photo-triggered T-rex under dilution (ca. 0.1
mg/mL). The SEC of the product after UV irradiation (Figure 4d)
showed a trace similar to that of Cuni (Figure 2g). Moreover,
MALDI-TOF mass spectrum (Figure S7c) showed a series of
peaks nearly identical to those of Cuni (Figure S7b). Remarkably,
these results demonstrate that ultrasound irradiation does not
cause ill-defined main chain scission but cause site-specific and
sacrificial cleavage of the covalent bond between the two
imidazoles in HABI similar to the mechanophore reported in the
literature.[16] It is also noteworthy that both of mechanical- and
photo-stimuli dissociate polymer chains with mechanistically
different but complemental principles and we are able to reset the
MW of Cmix through photo-triggered T-rex in either case.
within 4 min after terminating the irradiation. The response of Cmix
is significantly faster than that of previously reported network
materials likely owing to its liquid nature, allowing effective
diffusion of TPIR end groups within the PDMS matrix.[4] Moreover,
as appeared in time-course plots of loss tangent (tan δ = G’’/G’),
liquid-like character of the UV irradiated material become further
conspicuous; the tan δ increased by the factor of 5 and became
almost 8 compared with those of the former ca. 1.6 (Figure 4f). To
further clarify the effect of MW on the response of rheological
properties upon UV irradiation, we prepared linear PDMS having
lophine end groups with longer chain length (Ll, Mn(NMR) =
20000) and cyclic PDMS synthesized therefrom (Cl, mix). Shift of
Mp from Ll (Figure S11a) to Cl, mix (Figure S11b) suggests that Cl,
mix is composed of about three Lls. The number of components is
quite less than the aforementioned Cmix (Figure 2b), which is
composed of about ten Ls (Figure 2a). Time-course plots of G’
and G’’ upon ON–OFF cycles of UV irradiation to Cl, mix showed
trends similar to those of Cmix but the response was less
prominent (Figure S12).This indicates the magnitude of the
change in MW upon T-rex is one of the decisive factors in the
present system.
In conclusion, we have established the methodology for
repeatedly
reconstructing
cyclic
MAs
triggered
by
In the third, UV irradiation to Cmix dramatically and
repeatedly changes its rheological properties under a solvent-free
isothermal condition with retaining liquid character of PDMS. As
was expected from flowable characteristic, Cmix shows loss
modulus (G’’) higher than storage modulus (G’) in the frequency
range of 1–10 Hz (Figure S10). This is typical behavior of liquid
materials. Time-course plots of G’ and G’’ upon ON–OFF cycles
of UV irradiation showed their sudden decreases and increases
(Figure 4e). Both of G’ and G’’ repeatedly decreased to converged
values within 1 min upon UV irradiation and completely reverted
photostimulation. Photo-triggered T-rex against in-chain HABI-
functionalized cyclic PDMSs enables reproduction of cyclic
PDMSs with a desired mixing state of ring sizes; from the uniform
monocyclic to the maximally broad polydispersed state depending
on the UV-irradiating condition (diluted, concentrated, or solvent-
free condition). The in-chain HABIs also enable sacrificial
dissociation of polymer chains upon the application of ultrasound.
While MW decreases to converge into its threshold upon
ultrasound irradiation, further photo-triggered T-rex enables
complete dissociation into L* and reverts, for example, back to
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unimolecularly cyclized PDMS under dilution. Moreover, T-rex
enables repeatable and dramatic change in rheological properties
of PDMS with retaining its liquid character. Given that PDMS is
known as an industrially important polymeric material, the concept
of T-rex developed here could be useful for applications ranging
from lubricants, greases, and adhesives.
[11] a) T. Yan, K. Schröter, F. Herbst, W. H. Binder, T. Thurn-
Albrecht, Sci. Rep. 2016, 6, 32356; b) T. Yan, K. Schröter, F.
Herbst, W. H. Binder, T. Thurn-Albrecht, Macromolecules 2017,
50, 2973-2985.
[12] J. Cortese, C. Soulié-Ziakovic, M. Cloitre, S. Tencé-Girault, L.
Leibler, J. Am. Chem. Soc. 2011, 133, 19672-19675.
[13] G. R. Coraor, L. A. Cescon, R. Dessauer, A. S. Deutsch, H. L.
Jackson, A. MacLachlan, K. Marcali, E. M. Potrafke, R. E. Read,
J. Org. Chem. 1971, 36, 2267–2272.
Acknowledgements
[14] P. A. May, J. S. Moore, Chem. Soc. Rev. 2013, 42, 7497-7506.
[15] M. M. Caruso, D. A. Davis, Q. Shen, S. A. Odom, N. R. Sottos,
S. R. White, J. S. Moore, Chem. Rev. 2009, 109, 5755-5798.
[16] K. L. Berkowski, S. L. Potisek, C. R. Hickenboth, J. S. Moore,
Macromolecules 2005, 38, 8975-8978.
We are grateful to Mr. Yuichi Shinozaki, Mr. Ryuta Kawanishi, Mr.
Ryuuichi Yoshida, and Mr. Sadayuki Tanaka (Anton Paar Japan
K.K.) for their kind support for the rheological analyses and to Prof.
Robert M. Waymouth (Stanford University) for helpful discussion.
Synchrotron radiation-SAXS measurements were performed
under the approval of the Photon Factory Program Advisory
Committee (Proposal No. 2017G124 S.H.). This work was
supported by JSPS Grant-in-Aid for Scientific Research on
Innovative Areas “Discrete Geometric Analysis for Materials
Design” (Grant Number 18H04479 S.H.) and JSPS KAKENHI
(Grant Numbers 16K14074 S.H., and 16H04032 T.T.)..
Keywords: polymers • cyclic polymers • photochemistry •
macromolecular architecture • rheology
[1]
a) D. Aoki, S. Uchida, T. Takata, Angew. Chem. Int. Ed. 2015,
54, 6770-6774; b) T. Ogawa, N. Usuki, K. Nakazono, Y.
Koyama, T. Takata, Chem. Commun. 2015, 51, 5606-5609; c)
T. Ogawa, K. Nakazono, D. Aoki, S. Uchida, T. Takata, ACS
Macro Lett. 2015, 4, 343-347; d) S. Valentina, T. Ogawa, K.
Nakazono, D. Aoki, T. Takata, Chem. - Eur. J. 2016, 22, 8759-
8762; e) T. Yamamoto, S. Yagyu, Y. Tezuka, J. Am. Chem. Soc.
2016, 138, 3904-3911.
[2]
[3]
a) K. Endo, Adv. Polym. Sci. 2008, 217, 121-183; b) H. R.
Kricheldorf, J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 251-
284; c) B. A. Laurent, S. M. Grayson, Chem. Soc. Rev. 2009,
38, 2202-2213; d) Z. Jia, M. J. Monteiro, J. Polym. Sci., Part A:
Polym. Chem. 2012, 50, 2085-2097.
a) M. Schappacher, A. Deffieux, Macromolecules 2011, 44,
4503-4510; b) M. Schappacher, A. Deffieux, J. Am. Chem. Soc.
2011, 133, 1630-1633.
[4]
[5]
S. Honda, T. Toyota, Nat. Commun. 2017, 8, 502.
T. Hayashi, K. Maeda, Bull. Chem. Soc. Jpn. 1960, 33, 565–
566.
[6]
[7]
B. G. G. Lohmeijer, G. Dubois, F. Leibfarth, R. C. Pratt, F.
Nederberg, A. Nelson, R. M. Waymouth, C. Wade, J. L. Hedrick,
Org. Lett. 2006, 8, 4683-4686.
a) H. Tanino, T. Kondo, K. Okada, T. Goto, Bull. Chem. Soc.
Jpn. 1972, 45, 1474-1480; b) T. Goto, H. Tanino, T. Kondo,
Chem. Lett. 1980, 9, 431-434.
[8] a) S. Horiuchi, F. Kagawa, K. Hatahara, K. Kobayashi, R. Kumai,
Y. Murakami, Y. Tokura, Nat. Commun. 2012, 3, 1308; b) Y.
Morita, T. Murata, S. Yamada, M. Tadokoro, A. Ichimura, K.
Nakasuji, J. Chem. Soc., Perkin Trans. 1 2002, 2598-2600.
[9]
J. Cortese, C. Soulié-Ziakovic, S. Tencé-Girault, L. Leibler, J.
Am. Chem. Soc. 2012, 134, 3671-3674.
[10] S. Chen, W. H. Binder, Acc. Chem. Res. 2016, 49, 1409-1420.
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Topology reset execution (T-rex):
Photo-triggered T-rex against in-chain
HABI-functionalized cyclic PDMSs
enables reproduction of cyclic PDMSs
with a desired mixing state of ring sizes;
from the uniform monocyclic to the
maximally broad polydispersed state
depending on the UV-irradiating
S. Honda,* M. Oka, H, Takagi, T. Toyota
Page No. – Page No.
Topology-Reset Execution:
Repeatable Post-Cyclization Re-
cyclization of Cyclic Polymers
condition. T-rex enables repeatable and
dramatic change in rheological properties
of PDMS with retaining its liquid state.
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