Abstract
<jats:title>Abstract</jats:title> <jats:p>The interest in solution crystallization techniques came as a response to polymer catalyst development. The work of Ziegler–Natta in the early 1950s made possible the production of new polyolefins with the incorporation of alpha olefin comonomers. The new resins, such as linear low‐density polyethylene (LLDPE), were not homogeneous in the distribution of short‐chain branches, and the average values did not correspond with resin properties. The understanding of the short‐chain branching distribution, also known as chemical composition distribution (CCD), became essential.</jats:p> <jats:p>The most promising approach to measure the CCD was through solution crystallization techniques, given the fact that polyolefins are semicrystalline polymers.</jats:p> <jats:p>Temperature rising elution fractionation (TREF) was the first successful technique to analyze the CCD. A few years later, a faster technique capable of analyzing various samples simultaneously was developed, crystallization analysis fractionation (CRYSTAF). Today, TREF has been optimized and new techniques such as dynamic crystallization (DC) and crystallization elution fractionation (CEF) have been developed. All these techniques provide information to optimize the resin microstructure for specific applications, and CCD has become the most discriminating feature in new copolymers, blends, and recyclates.</jats:p> <jats:p>When dealing with complex multireactor resins, full microstructure identification also requires analysis of the composition‐molar mass interdependence, known as the bivariate distribution, which is obtained by cross‐fractionation chromatography (CFC) combining TREF and gel permeation chromatography (GPC) in a separate technique.</jats:p>