# Temperature-Dependent Conformation Behavior of Isolated Poly(3-hexylthiopene) Chains

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Simulation Models and Details

#### 2.1. Molecular Dynamics Simulations

#### 2.2. Lennard–Jones Model Polymer

#### 2.3. Atomistic Poly(3-hexylthiopene) Model

#### 2.4. Coarse Grained Martini Poly(3-hexylthiopene) Model

## 3. Results

#### Lennard–Jones Model Polymers

## 4. Poly(3-hexylthiopene) (P3HT)

#### 4.1. Atomistic P3HT

#### 4.2. Martini P3HT in Vacuum

#### 4.3. Martini P3HT in THF Solvent

## 5. Discussion and Conclusions

## Supplementary Materials

**a**) Side view with P3HT side chains going in and out of the plane. (

**b**) Top view along the length of P3HT. (

**c**) $\pi -\pi $ stacking along with P3HT stacking along y-axis (

**d**) Schematic of P3HT central portion. Figure S3: Torsional population at 300K for P3HT chains with n = 13, 20, 30 as a function of (

**a**) $\alpha $, (

**b**) ${\beta}_{1}$ and (

**c**) ${\beta}_{2}$ which show highest populations approximately at 180, 90 and 180 degrees respectively. Figure S4: Structural phase diagrams with respect to bending constant of our LJ model system. The conformation labels here follow the notation of Zierenberg et al (2016), and thus deviate from the ones used in the main text: R(random coil), H (hairpin), D3 (rod like bundle), K (toroids), C (globular). Figure S5: The state diagram of semiflexible polymers for chain stiffness (bending potential) as a function of inverse of temperature obtained from our MD simulations of an LJ model polymer. Figure S6: For Atomistic P3HT with n = 200: (

**a**) $\langle {S}^{2}\rangle $ as a function of temperature. (

**b**) ${S}^{2}$ distribution as a function of temperature. This figure corresponds to the data of Figure 5 of the paper. Figure S7: For Martini CG P3HT in vacuum with n = 200: (

**a**) $\langle {S}^{2}\rangle $ as a function of temperature. (

**b**) ${S}^{2}$ distribution as a function of temperature. This figure corresponds to the data of Figure 7 of the paper. Figure S8: For Martini CG P3HT in THF solvent with n = 200: (

**a**) $\langle {S}^{2}\rangle $ i as a function of temperature. (

**b**) ${S}^{2}$ distribution as a function of temperature. This figure corresponds to the data of Figure 9 of the paper. Figure S9: Typical toroids, globules and bundles found in the atomistic P3HT simulations at 300K. Figure S10: Typical toroids, globules and bundles found in the martini CG P3HT vacuum simulations at 200K-250K. Figure S11: Typical toroids, globules and bundles found in the martini CG P3HT in THF solvent at 300K. Figure S12: ${D}_{m}ax$ Distribution for different temperatures of Martini CG P3HT in THF solvent with (

**a**) n = 68 and (

**b**) n = 112. Figure S13: Box length for different simulations at 300 K.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Abbreviations

P3HT | Poly(3-hexylthiopene) |

THF | Tetrahydrofuran |

MD | Molecular Dynamics |

ATB | Automated Topology Builder and Repository |

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**Figure 1.**Schematic illustration of P3HT in (

**a**), all-atom model in (

**b**) and 6-site Martini CG in (

**c**).

**Figure 2.**(

**a**) Mean squared radius of gyration $\langle {S}^{2}\rangle $ as a function of temperature for a LJ polymer with $n=200$. The stiffness is tuned by the non bonded parameter ${C}_{6}$ in $\frac{\mathrm{kJ}}{\mathrm{mol}\phantom{\rule{4.pt}{0ex}}{\mathrm{nm}}^{6}}$. (

**b**) Similar to (

**a**), but the stiffness is tuned by varying the bending potential ${k}^{\theta}$ in $\frac{\mathrm{kJ}}{\mathrm{mol}\phantom{\rule{4.pt}{0ex}}{\mathrm{rad}}^{2}}$. (

**c**) Average maximum distance between two monomers ${D}_{max}$ as a function of temperature for an LJ polymer where the stiffness is set by ${C}_{6}$. (

**d**) Similar to (

**c**) but tuning the bending potential.

**Figure 3.**Distribution of ${S}^{2}$ for (

**a**) stiff (${C}_{6}=0.0000$), (

**b**) semiflexible(${C}_{6}=0.00045$), and (

**c**) flexible (${C}_{6}=0.001$) polymers. Distribution of ${D}_{max}$ (

**d**) stiff (${C}_{6}=0.0000$), (

**e**) semiflexible (${C}_{6}=0.00045$), and (

**f**) flexible (${C}_{6}=0.001$) polymers.

**Figure 4.**(

**a**) From left to right illustration of toroid, bundle, random coil, ring and hairpin. (

**b**) Color coded final conformations at a range of temperature for 50 simulations at different ${C}_{6}$ values. (

**c**) ${D}_{max}$ distribution of the above five mentioned structures.

**Figure 5.**The maximum distance between monomers for the atomistic P3HT model in vacuum at different temperatures. (

**a**) The averaged ${D}_{max}$ as a function of temperature shows a sigmoidal increase at very high and a slight increase towards low temperatures (inset). (

**b**) The ${D}_{max}$ distributions at different temperatures exhibit three clear peaks corresponding to toroids, tight coils and bundles (from left to right) which are illustrated in (

**c**).

**Figure 6.**(

**a**) Color coded final conformations at a range of temperature for 50 simulations for atomistic P3HT in vacuum. (

**b**) ${D}_{max}$ distributions used for toroid, globules, and bundles.

**Figure 7.**The maximum distance between monomers for the Martini model of P3HT in vacuum. (

**a**) Averaged ${D}_{max}$ as a function of temperature. (

**b**) Distributions at various temperatures. (

**c**) Illustration of the corresponding conformations: toroids, tight globules and bundles.

**Figure 8.**(

**a**) Color coded final conformations at a range of temperature for 50 simulations for the Martini model of P3HT in a vacuum. (

**b**) ${D}_{max}$ distributions used for toroid, globules, and bundles.

**Figure 9.**The maximum distance between monomers for the Martini model of P3HT in THF solvent. (

**a**) Averaged ${D}_{max}$ as a function of temperature. (

**b**) Distributions at various temperatures. (

**c**) Illustration of the corresponding conformations: toroids, tight globules and bundles.

**Figure 10.**(

**a**) Color coded final conformations at a range of temperature for 50 simulations for the Martini model of P3HT in THF solvent. (

**b**) ${D}_{max}$ distributions used for toroid, globules and bundles.

**Figure 12.**The maximum distance between monomers for the Martini model of P3HT with $n=68$ and $n=112$ in THF solvent.

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**MDPI and ACS Style**

Pantawane, S.; Gekle, S.
Temperature-Dependent Conformation Behavior of Isolated Poly(3-hexylthiopene) Chains. *Polymers* **2022**, *14*, 550.
https://doi.org/10.3390/polym14030550

**AMA Style**

Pantawane S, Gekle S.
Temperature-Dependent Conformation Behavior of Isolated Poly(3-hexylthiopene) Chains. *Polymers*. 2022; 14(3):550.
https://doi.org/10.3390/polym14030550

**Chicago/Turabian Style**

Pantawane, Sanwardhini, and Stephan Gekle.
2022. "Temperature-Dependent Conformation Behavior of Isolated Poly(3-hexylthiopene) Chains" *Polymers* 14, no. 3: 550.
https://doi.org/10.3390/polym14030550