# Glass Transition Behavior of Wet Polymers

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experimental Methods

#### 2.1. Material Synthesis

#### 2.2. Treatment by IPA

^{−4}g. This step is to ensure a homogenous distribution of solvents in specimens. For each measurement, three specimens were repeated. The swelling ratio ${\mathrm{S}}_{\mathrm{w}}$ is then defined as

#### 2.3. Dynamic Temperature Sweep Tests

#### 2.4. Dynamic Frequency Sweep Tests

## 3. Results and Discussions

^{3}, while IPA has a density of 0.785 g/cm

^{3}. Based on the swelling results shown in Figure 4, for acrylate-based polymer with 2 wt.% crosslink density the ratio of the volume in the equilibrium swelling state and the dry state is around 3.7, while that for polymers with 20 wt.% crosslink density is around 1.7. The value of J and the corresponding density of other wet polymers can also be calculated based on the assumption of the volumetric incompressibility for mixture. Thus, the measured value is generally consistent with the above relationship. There are few theories to relate the glassy modulus of the wet polymers with dry polymers. Our results can potentially be used to validate a future developed theory. The value for the relaxation breadth $\mathsf{\alpha}$ continuously decreases with increasing solvent concentration for both polymers. A smaller value of $\alpha $ indicates a broader relaxation spectrum. Thus, solvents can expand the breadth of the relaxation spectrum. So far, few works have been performed to investigate the effects of solvent on the relaxation spectrum both in experimental and theoretical aspects. One possible explanation is that extra chemical or physical bonding may be formed between solvent and polymer molecules. The strength of intermolecular interaction in polymers can be further affected by the newly formed bonding, which further results in a change in the relaxation responses [27]. In addition to solvents, some works [28,29] also show that the relaxation spectrum of dry polymers can be changed by mechanical deformation.

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**The storage modulus as a function of frequency for dry polymers with 2 wt.% crosslink density (

**a**) measured at different temperatures, and (

**b**) shifted to form a master curve.

**Figure 2.**The temperature-dependent shift factor ${a}_{\mathrm{T}}\left(T\right)$ for dry polymers with 2 wt.% crosslink density at (

**a**) the reference temperature ${T}_{0}$ and (

**b**) the glass transition temperature ${T}_{\mathrm{g}}^{\mathrm{ref}}$.

**Figure 5.**The storage modulus as a function of temperature of (

**a**) polymers with 2 wt.% crosslinking density and (

**b**) 20 wt.% crosslink density and treatment in isopropyl alcohol (IPA) for different times.

**Figure 6.**The storage modulus for polymers with 2 wt.% crosslink density and treatment by IPA for (

**a**) 1 h and (

**c**) 10 h, and the master curve for (

**b**) 1 h and (

**d**) 10 h.

**Figure 7.**The storage modulus for polymers with 20 wt.% crosslink density and treatment by IPA for (

**a**) 1 h and (

**c**) 10 h, and the master curve for (

**b**) 1 h and (

**d**) 10 h.

**Figure 8.**The temperature-dependent shift factor for polymers with (

**a**) 2 wt.% and (

**b**) 20 wt.% crosslink density.

**Figure 9.**Measured and fitted master curve for polymers with 2 wt.% crosslink density and subjected to (

**a**) 1 h and (

**b**) 10 h immersion time in IPA.

**Figure 10.**Measured and fitted master curve for polymers with 20 wt.% crosslink density and subjected to (

**a**) 0 h, (

**b**) 1 h, (

**c**) 2 h and (

**d**) 10 h immersion time in IPA.

Name of Samples | The Mass Ratio (tBA:PEGDMA:DMPA) |
---|---|

Acrylate-based polymer with 2 wt.% crosslink density | 98:2:0.2 |

Acrylate-based polymer with 20 wt.% crosslink density | 80:20:0.2 |

**Table 2.**Parameters of Williams–Landel–Ferry (WLF) constants for polymers with 2 wt.% crosslink density.

Parameter | Dry | 30 min | 1 h | 5 h | 10 h | Physical Significance |
---|---|---|---|---|---|---|

${T}_{0}$ ($\mathbb{C}$) | 75 | 10 | 0 | −5 | −25 | The reference temperature |

${C}_{1}^{0}$ | 4.70 | 5.90 | 7.78 | 25.52 | 24.62 | First WLF constant at ${T}_{0}$ |

${C}_{2}^{0}$ ($\mathbb{C}$) | 62.34 | 64.92 | 79.47 | 187.80 | 144.08 | Second WLF constant at ${T}_{0}$ |

${T}_{\mathrm{g}}^{\mathrm{ref}}$ ($\mathbb{C}$) | 40 | −25 | −45 | −70 | −80 | Glass transition temperature |

${C}_{1}^{\mathrm{g}}$ | 10.72 | 12.80 | 17.94 | 39.03 | 39.82 | First WLF constant at ${T}_{\mathrm{g}}^{\mathrm{ref}}$ |

${C}_{2}^{\mathrm{g}}$ ($\mathbb{C}$) | 27.34 | 29.92 | 34.47 | 122.80 | 89.08 | Second WLF constant at ${T}_{\mathrm{g}}^{\mathrm{ref}}$ |

Parameter | Dry | 1 h | 2 h | 10 h | Physical Significance |
---|---|---|---|---|---|

${T}_{0}$ ($\mathbb{C}$) | 60 | 15 | 10 | −10 | The reference temperature |

${C}_{1}^{0}$ | 5.31 | 10.14 | 7.81 | 8.80 | First WLF constant at ${T}_{0}$ |

${C}_{2}^{0}$ ($\mathbb{C}$) | 54.06 | 79.69 | 73.84 | 82.33 | Second WLF constant at ${T}_{0}$ |

${T}_{\mathrm{g}}^{\mathrm{ref}}$($\mathbb{C}$) | 30 | −20 | −25 | −55 | Glass transition temperature |

${C}_{1}^{\mathrm{g}}$ | 11.93 | 18.08 | 14.85 | 19.41 | First WLF constant at ${T}_{\mathrm{g}}^{\mathrm{ref}}$ |

${C}_{2}^{\mathrm{g}}$ ($\mathbb{C}$) | 24.06 | 44.69 | 38.84 | 37.33 | Second WLF constant at ${T}_{\mathrm{g}}^{\mathrm{ref}}$ |

Parameter | Dry | 30 min | 1 h | 5 h | 10 h | Physical Significance |
---|---|---|---|---|---|---|

${E}^{\mathrm{neq}}$ (MPa) | 872 | 527 | 498 | 170 | 89 | The glassy moduli |

${E}^{\mathrm{eq}}$ (MPa) | 0.58 | 0.51 | 0.47 | 0.20 | 0.15 | The rubbery moduli |

$\mathsf{\tau}\left({10}^{-9}\mathrm{s}\right)$ | 2100 | 2150 | 80 | 0.010 | 0.074 | Stress relaxation time at $\mathrm{T}={T}_{0}$ |

$\mathsf{\alpha}$ | 0.7 | 0.68 | 0.58 | 0.26 | 0.28 | Breadth of relaxation spectrum |

Parameter | Dry | 1 h | 2 h | 10 h | Physical Significance |
---|---|---|---|---|---|

${E}^{\mathrm{neq}}$ (MPa) | 1438 | 805 | 686 | 399 | The glassy moduli |

${E}^{\mathrm{eq}}$ (MPa) | 3.53 | 3.46 | 3.43 | 3.25 | The rubbery moduli |

$\mathsf{\tau}\left({10}^{-9}\mathrm{s}\right)$ | 9270 | 9200 | 1690 | 30 | Stress relaxation time at $\mathrm{T}={T}_{0}$ |

$\mathsf{\alpha}$ | 0.72 | 0.66 | 0.66 | 0.42 | Breadth of relaxation spectrum |

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Li, H.; Xiao, R. Glass Transition Behavior of Wet Polymers. *Materials* **2021**, *14*, 730.
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Li H, Xiao R. Glass Transition Behavior of Wet Polymers. *Materials*. 2021; 14(4):730.
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Li, Hai, and Rui Xiao. 2021. "Glass Transition Behavior of Wet Polymers" *Materials* 14, no. 4: 730.
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