超高分子量ポリエチレンの初期および長期の微細構造の変化の決定は,きれいなおよびピレニル改変フィルムの描画によって誘発されます
Chuping Luo1, Teresa D Z Atvars, Pavla Meakin
1Department of Chemistry, Georgetown University, Washington, D.C. 20057-1227, USA.
Journal of the American Chemical Society
|September 25, 2003
まとめ
新しいモデルは,ゲル結晶化超高分子量ポリエチレン (UHMWPE) がどのように変形するかを説明しています. 微細繊維の動きは結晶性を低下させ,低引力比で自由体積を増加させ,材料の特性に影響を与えます.
科学分野:
- ポリマーサイエンスの科学
- マテリアルサイエンス 材料科学
- 物理化学 物理化学
背景:
- 超高分子量ポリエチレン (UHMWPE) は,材料研究において極めて重要です.
- UHMWPEの変形メカニズムを理解することは,その特性を最適化するために不可欠です.
- ゲル結晶化UHMWPEフィルムは,加工によって影響を受けたユニークな特徴を示しています.
研究 の 目的:
- ゲル結晶化UHMWPEフィルムの変形過程を,高引力比 (DR) まで調査する.
- 様々なスペクトロスコピーおよび熱技術を使用して,構造的および動的性質を相関させる.
- 実験的証拠に基づいたUHMWPE変形のための新しいモデルを提案する.
主な方法:
- X線微分法 (XRD),微分スキャニング熱計法 (DSC),陽子滅亡終生スペクトル法 (PALS) が使用されました.
- ピレン・ドーピングと光スペクトロスコピーは分子動態を調査した.
- N,N-ジメチラニリン (DMA) の拡散は,ドーピングされたフィルムで測定されました.
主要な成果:
- マイクロフィブリル"ストレッチ"と"フリップ"の動きを含む新しい変形モデルが提案されました.
- 低引出比は結晶性の低下と平均自由量の増加につながった.
- 高引力比は結晶性の増加,鎖の硬化,およびリラックスプロセスの変化をもたらした.
結論:
- 提案されたモデルは,結晶性および自由体積の観測された変化をうまく説明しています.
- 変形は,UHMWPEのリラックス行動と分子移動性に大きく影響します.
- この研究は,UHMWPEの形態学と変形機構の包括的な理解を提供します.
関連する概念動画
Polymer Classification: Architecture
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
Polymer Classification: Crystallinity
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Polymer Classification: Stereospecificity
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
Molecular Weight of Step-Growth Polymers
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
Determination of Molar Masses of Polymers I
Polymerization produces macromolecules with a range of chain lengths due to the random nature of molecular growth processes. As chains form and terminate at different stages, a single polymer sample contains molecules of varying sizes rather than a uniform structure. This variability is described using average molar masses and distribution-related parameters, which together provide a comprehensive understanding of polymer characteristics.The distribution of molar masses plays a critical role in...


