Confined crystallization of polymers within anodic aluminum oxide templates

Abstract

In this article, a review of recent literature on confined crystallization within nanoporous anodic aluminum oxide (AAO) templates is presented. For almost all infiltrated polymeric materials, crystal orientation within the nanopores is a function of pore diameter. T c and T m usually decrease and are a function of pore size. When no pore interconnection remains, the crystallization occur at large supercoolings in heterogeneity free environments. Hence, the nucleation mechanism changes from heterogeneous to surface or homogeneous nucleation. The crystallization kinetics of infiltrated polymers should be close to first order, since in confined environments nucleation is the determining step of the overall crystallization and Avrami indexes (n) of 1 (or lower in some cases) should be obtained. Examples are provided where these conditions have been met and first order kinetics (n 5 1) were measured as opposed to higher orders (n 5 324) for the same polymer in the bulk. INTRODUCTIONThe crystallinity content and the superstructural morphology control, to a large degree, the thermal, mechanical, and electrical properties of polymers, and in consequence their practical applications. A full understanding of polymer crystallization will provide an effective tool to predict and adjust the properties of semicrystalline polymers according to the application sought.

Crystallization and orientation of isotactic poly(propylene) in cylindrical nanopores

“…Additionally, fractionated crystallization, possible here for iPP‐40, is often observed when the number of isolated microdomains is larger than the number of heterogeneities in the bulk polymer. Studies of other polymers inside AAO have shown that fractionated crystallization could also be caused by the presence of a polymer surface layer …”

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

“…Such a large difference normally leads to statistically clean droplets and a large depression in their crystallization temperature. For more details on the process of fractionated crystallization, the reader is referred to the literature [3,[101][102][103][104][105].…”

“…It is likely that it corresponds to the crystallization of a fraction of heterogeneity-free PP droplets. Its exact origin is debatable because it could correspond to the crystallization of a group of clean droplets whose nucleation either starts from the surface of the droplets (or the interface between PP and PS) or by homogeneous nucleation inside the PP droplets (see [3,[101][102][103][104][105]). …”

Crystallization of polymer chains confined in nanodomains

“…spatial confinement, and excellent review articles are now available for the crystallization behavior of such confined chains and resulting morphology formed in the system [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The typical nanodomains to confine polymer chains are provided by micelles in solution [3,4,13,17], aluminum anodic oxides (AAOs) [7,11,[13][14][15]18], or microdomain structures (i.e., various nanodomains formed by the microphase separation of block copolymers) [1,2,5,6,[8][9][10][11][12][13][14]16] (Fig.…”

“…The typical nanodomains to confine polymer chains are provided by micelles in solution [3,4,13,17], aluminum anodic oxides (AAOs) [7,11,[13][14][15]18], or microdomain structures (i.e., various nanodomains formed by the microphase separation of block copolymers) [1,2,5,6,[8][9][10][11][12][13][14]16] (Fig. 1), where it is found that the crystallization behavior, final crystallinity, and crystal orientation of confined chains are extremely different from those of bulk homopolymers.…”