Supplementary Information

Expandable Temperature-Responsive Polymeric Nanotubes

Shintaro Kawano and Marek W. Urban*

School of Polymers and High Performance Materials

Shelby F. Thames Polymer Science Research Center

The University of Southern Mississippi

Hattiesburg, MS, 39406, USA

Supplementary Discussion

Figure S-1 illustrates ATR FT-IR spectra of PNNTs with the bands at 1652 and 1560 cm-1

due to amide I and amide II functionalities confirming PNNT polymerization1. To support IR

evidence for PNIPAM polymerization 1H-NMR spectra of PNNTs shown in Figure S-2 were

recorded. The resonances labeled a-d and 1-8 in PNIPAM and PL components, respectively,

correspond to respective structural features, again indicating polymerization of NIPAM

monomer within PL bilayers. Table S-1 summarizes relevant 1H-NMR resonances. Figure S-3,

Traces A and B, illustrates Raman spectra of PNNTs and CL-PNNTs, respectively. The presence

of the bands at 1550 and 2200 cm-1

in CL-PNNTs (Trace B) shows the formation of C=C/CΞC

crosslinks2. Figure S4 illustrates TEM images of CL-PNNTs at 25 (A) and 40 (B) ℃. In

contrast to PNNTs (Figure 2), CL-PNNTs do not exhibit dimensional changes as a function of

temperature.

In an effort to establish what molecular entities are responsible for thermal expansion and

shrinkage of PNNTs ATR FT-IR spectra of thin films cast from PNNT and PLNT dispersions

were measured as a function of temperature. Figure S5, Traces A-F illustrate the spectra of (A)

PNIPAM- 25℃, (B) PNIPAM- 40℃, (C) PLNT- 25℃, (D) PLNT- 40℃, (E) PNNT- 25℃, and

(F) PNNT- 40℃. Traces A and B represent the PNIPAM spectra recorded at 25 and 40 ℃, and

show that the bands at 1646 cm-1

and 1544 cm-1

due to amide I (-C=O) and amide II (N-H)

groups, respectively, are affected by temperature changes. The amide I band intensity decreases,

whereas the amide II shifts from 1542 to 1536 cm-1

at 40 ℃ due to partial inter-amide chain

dissociation above LCST leading to coil-to-globule transitions1, 3, 4

. To determine the

temperature effect on PLNTs structural changes, Traces C and D represent PLNT spectra

recorded at 25 and 40 ℃, respectively. As seen, no spectroscopic changes are detected,

indicating no temperature affect on PLNTs. Traces E and F show ATR FT-IR spectra of PNNTs

recorded at 25 and 40 ℃, respectively. As expected, the presence of amide I and amide II bands

is detected, but significant broadening in the 1662-1652 cm-1

region (Traces E) at 25 ℃ (amide

I band) is minimized at 40 ℃ (Traces F). Also, the 1560 cm-1

band in Trace E shifts to 1540

cm-1

. These results suggest that below LCST (25 ℃ spectra) PNIPAM and PL bilayers in

PNNTs interact via amide groups of PNIPAM and acyl C=O groups of PL bilayers5. These

interactions are interrupted above LCST (40 ℃ data).

To identify structural features and differences in between PNIPAM and PL entities within

PNNTs as a function of temperature series of Raman spectra in the 25-45 ℃ range were

collected: PLNTs (Figure 6-1), CL-PLNTs (Figure 6-2) and CL-PNNTs (Figure 6-3). For

reference, neat PNIPAM (Figure 6-4) specta were also examined, which is known for minute

changes below and above the LCST4. As show and agrees with the literature, only notable

differences are in the C-C isopropyl and C-H asymmetrical deformation bands at 1132 and 1457

cm-1

which slightly decrease above LCST. Also, the bands at 1346 and 1391 due to C-H

symmetrical deformations increase, indicating that the C-H vibrations of isopropyl chains

become symmetric above LCST.

Figure S6-1, Traces A-D illustrate Raman spectra of neat PLNTs in the same temperature

change. As temperature increases, the following spectroscopic changes are detected: the bands

at 1060, 1127 (C-C skeletal) and 1300 (CH2 rock) cm-1

diminish, whereas the 1420 cm-1

band

due to CH2 scissoring shifts to 1429 cm-1

. At the same time, the band due to CH2 deformations

at 1337 cm-1

increases. These observations are in agreement with the literature2 and indicate that

initially orthorhombic packing of hydrophobic layers became looser at above LCST.

The same experiments conducted on CL-PLNTs show no spectroscopic changes in the C-C

skeletal and CH2 scissoring vibrations, although the band intensities of 1300 cm-1

due to CH2

rock normal modes slightly decrease. This is illustrated in Figure S6-2, Traces A-D. As we

recall, Raman spectra of neat PLNTs (Figure S6-1) showed that the 1420 cm-1

band due to CH2

scissoring vibrations shifts to 1429 cm-1

. It should be also noted that notable although not strong

intensity increase is detected in the C=C vibrations at 1514 cm-1

and CΞC at 2111 cm-1

, which

are likely attributed to residual crosslinking at elevated temperatures.

As we recall Figure 3A of the Main Doccument, Traces A-D, illustrate Raman spectra of

PNNT recorded in the 25-45 ℃ range. As seen, significant increase of the bands at 1137 and

1268 cm-1

due to C-C isopropyl and amide ΙΙΙ (C-C-N; coupling between amide and isopropyl),

at elevated temperature was observed. This observation is attributed to strong intra-molecular

interactions of isopropyl chains of PNIPAM, indicating that PNIPAM globular structures are

formed upon elimination of hydrophilic zone interactions between PL and PNIPAM. Also, the

band at 1458 cm-1

(isopropyl C-H asymmetrical deformation) decreases due to lower symmetry

of isopropyl side chains resulting from coil-to-globular transition. The PL component of PNNTs

exhibits the same spectroscopic changes as a function of temperature as that of neat PLNT

(Figure S6-1).

Figure S6-3, Traces A-D, illustrates Raman spectra of CL-PNNTs recorded at 25, 35, 40

and 45 ℃, respectively, and show that crosslinking reactions of the PL bilayer portion of

CL-PNNTs do not affect PNIPAM components, as manifested by no spectroscopic changes.

However, the spectral changes shown in Figure S6-3 illustrate that the intensity of the bands at

1127 cm-1

(C-C skeletal) and 1300 cm-1

(CH2 rock) decrease, whereas the band at 1337 cm-1

(CH2 rock) increases. At the same time, the band at 1420 cm-1

(CH2 scissoring) due to

orthorhombic packing shifts to 1429 cm-1

. These changes are attributed to PL bilayers and

indicate that orthorhombic packing of PL bilayers is perturbed, whereas conformational changes

of PNIPAM in CL-PNNTs are restricted.

Thermal analysis of PNIPAM solutions as well as PLNT and PNNT dispersions was

conducted in two sets of DSC experiments which were conducted at heating rates of 0.5 and

5℃/min. Figure S7 illustrates DSC thermograms recorded at 0.5℃/min for PNIPAM solutions

(A) and PNNT dispersions (B). As shown, two endothermic transitions are observed at 32.1

(Trace A) and 37.1 (Trace B) ℃, which are attributed to LCST transitions of PNIPAM and

PNNT, respectively. While the 32.1℃ transition of PNIPAM agrees with the literature6, the

transition in PNNT detected at 37.1℃ is attributed to PL bilayer PNIPAM interactions. When

PNNT was analyzed at 5℃/min heating rate, the endothermic transition at 43℃ was detected,

as shown in Figure S7, Trace C. For reference purpose, Trace D of Figure S7 illustrates PLNT

thermogram recorded at 5℃/min and show the transition at 43.8℃7. These observations indicate

that the interaction of PNIPAM with PL bilayers shifts transition temperatures, as reflected in

spectroscopic analysis as a function of temperature.

Figure S1. ATR-FT-IR spectra of a thin layer film cast from PNNT dispersions.

Figure S2. 1H NMR spectra of PNNTs measured in CDCl3.

Table S1. 1H NMR resonances observed in PNNTs.

Figure S3. Raman spectra of thin layered films of PNNTs (a) and CL-PNNTs (b) cast on a Au

substrate obtained from aqueous dispersions.

Figure S4. TEM images of CL-PNNTs as a function of temperature; A- 25 ℃, B- 40 ℃.

Figure S5. ATR-IR spectra in the 1700-1500 cm-1

region of cast films at 25 and 40℃; A -PNIPAM-

25℃, B -PNIPAM- 40℃, C -PLNT- 25℃, D -PLNT- 40℃, E -PNNT- 25℃, F -PNNT- 40℃.

Figure S6-1. FT-Raman spectra in the 1000-1700 cm-1 region of PLNT recorded as a function of temperature at

25 (A), 35 (B), 40 (C) and 45 (D) ℃.

Figure S6-2. FT-Raman spectra in the 1000-1700 cm-1 region of CL-PLNT recorded as a function of temperature

at 25 (A), 35 (B), 40 (C) and 45 (D) ℃.

Figure S6-3. FT-Raman spectra in the 1000-1700 cm-1 region of CL-PNNT recorded as a function of

temperature at 25 (A), 35 (B), 40 (C) and 45 (D) ℃.

Figure S6-4. FT-Raman spectra in the 1000-1700 cm-1 region of PNIPAM recorded as a function

of temperature at 25 (A), 30, (B), 35 (C), 40 (D) and 45 (E) ℃.

Figure S7. Series of DSC thermograms of PNIPAM solution (A), PNNT (B and C) and PLNT (D) dispersions at

heating rate of 0.5 ℃/min from 10 to 40℃ (A and B), and 5 ℃/min from 10 to 70℃ (C and D).

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