Letter reSeArCH
MEthodS
General procedure for living APEX polymerization. The general experimen-
tal procedure of living APEX polymerization of I and M with a ratio of 1:100
(described in Fig. 1a) is as follows. Initiator I (0.40 mg, 2.25 μmol), monomer
M (100 mg, 225 μmol), Pd(OCOCF 3 ) 2 (75.1 mg, 225 μmol), AgSbF 6 (77.6 mg,
450 μmol), o-chloranil (110 mg, 450 μmol) and 1,2-dichloroethane (2.3 ml) are
added into a 5-ml Schlenk tube containing a magnetic stirring bar under a N 2
atmosphere. After stirring the mixture at 80 °C for 12 h, the reaction mixture is
cooled to room temperature, passed through a short pad of silica gel and then
washed with a metal scavenger with CH 2 Cl 2. The solvent is removed in vacuo
to give the crude product, and SEC analysis shows the formation of a polymer
with Mn = 3.2 × 104 Da and Đ = 1.25. Purification by SEC with chloroform as
an eluent affords fjord-type GNR 2 as a black powder (88.0 mg, 85% yield). The
living APEX polymerization reactions of I and M with ratios 1:10, 1:50, 1:300,
1:500 are conducted under the same reaction conditions to afford GNR 2 with
Mn = 2.9 × 103 Da (Đ = 1.25), 1.3 × 104 Da (1.23), 9.7 × 104 Da (1.22) and
1.5 × 105 Da (1.22), respectively.
General procedure for the transformation of fjord-type GNR 2 to armchair-type
GNR 8. Fjord-type GNR 2 (30 mg, 30 μmol, Mn = 3.2 × 104 Da and Đ = 1.21) and
CH 2 Cl 2 (120 ml) are added into a 200-ml two-necked round-bottom flask con-
taining a magnetic stirring bar under a N 2 atmosphere. A suspension of iron(III)
chloride (1.75 g, 10.8 mmol, 7 equiv. against hydrogen atoms on fjord-regions,
estimated from Mn) in nitromethane (15 ml) is added to this solution. After stir-
ring the mixture at room temperature for 72 h, the reaction is quenched by the
addition of methanol to form a dark red precipitate. Filtration by suction and
intensive washing with methanol give armchair-type GNR 8 as a dark red pow-
der (28.5 mg, 98% yield). The SEC analysis shows the formation of GNR 8 with
Mn = 2.4 × 104 Da and Đ = 1.32.
Determination of Mn, Mw and Đ of synthesized GNRs. The molecular weight
(Mn and Mw) and Đ (Mw/Mn) of all synthesized GNRs were measured by SEC
using a Shimadzu Prominence 2000 instrument equipped with two in-line lin-
ear polystyrene gel columns (TOSOH TSKgel Multipore HXL-M SEC columns
7.8 mm × 300 mm) at 40 °C, and tetrahydrofuran containing 0.1 wt% tetra-n-
butylammonium bromide was used as the eluent at a flow rate of 1.0 ml min−^1.
The molecular weight calibration curve was obtained with standard PS (TOSOH
TSKgel PS standard).
STM characterization of GNRs 2 and 8. A low-temperature STM (Unisoku, USS-
10092LSC) was used to characterize the morphology of the GNR samples prepared
on HOPG. The sample substrates were prepared by drop-casting solutions of GNR
2 (~0.01 mg mL−^1 , Mn = 1.5 × 105 Da, Đ = 1.22) or of 8 (~0.0015 mg mL−^1 ,
Mn = 2.4 × 104 Da, Đ = 1.32) in 1,2,4-trichlorobenzene on HOPG; the solutions
were heated at 363 K, followed by evaporation of 1,2,4-trichlorobenzene at 363 K
under air. STM images were taken in constant current mode under ultrahigh
vacuum at 78 K (liquid N 2 cooling).
AFM characterization of GNR 2. A solution of about 0.01 mg mL−^1 fjord-type
GNR 2 with Mn = 3.4 × 104 Da and Đ = 1.21 in 1,2,4-trichlorobenzene was
drop-casted on the HOPG substrate, which was heated on a hot plate at 393 K
under air. After settling for several tens of seconds, the solvent was removed
by blowing N 2 gas in one direction and further dried for 3 min at 393 K. AFM
(Bruker, DimensionFastScan) images were taken in tapping mode in air at room
temperature.Data availability
The datasets generated and/or analysed during the current study are available from
the corresponding authors on reasonable request.