First Clear-Cut Experimental Evidence of a Glass Transition in a Polymer with Intrinsic Microporosity: PIM‑1

Polymers
with intrinsic microporosity (PIMs) represent a novel,
innovative class of materials with great potential in various applications
from high-performance gas-separation membranes to electronic devices.
Here, for the first time, for PIM-1, as the archetypal PIM, fast scanning
calorimetry provides definitive evidence of a glass transition (Tg = 715 K, heating rate 3 × 104 K/s) by decoupling the time scales responsible for glass transition
and decomposition. Because the rigid molecular structure of PIM-1
prevents any conformational changes, small-scale bend and flex fluctuations
must be considered the origin of its glass transition. This result
has strong implications for the fundamental understanding of the glass
transition and for the physical aging of PIMs and other complex polymers,
both topical problems of materials science.

固有微孔聚合物（Polymers with Intrinsic Microporosity, PIMs）是一类极具创新性的新型材料，在高性能气体分离膜、电子器件等诸多领域均具备巨大应用潜力。本研究首次通过快速扫描量热法（fast scanning calorimetry），分离玻璃化转变与分解所对应的时间尺度，为作为典型原型的固有微孔聚合物PIM-1提供了玻璃化转变（glass transition）的确凿证据（Tg = 715 K，升温速率3×10^4 K/s）。由于PIM-1的刚性分子结构阻碍了任何构象变化，因此其玻璃化转变的起源应归因于小规模的弯曲与挠曲波动。该研究成果对于深化对玻璃化转变的基础认知，以及固有微孔聚合物与其他复杂聚合物的物理老化（physical aging）研究均具有重要意义，而上述两类问题均为材料科学领域的前沿研究课题。