Polymer Crystallization Processes as Seen from the Growth Front’s Perspective

Abstract

A critical analysis is presented regarding the possible processes that determine polymer crystal growth, based mostly on the analysis of the structure and morphology of polymer single crystals. This ''forensic'' analysis suggests that the interaction of the depositing stem with the growth front is the determining factor in the whole crystallization process, irrespective of any previous (pre)organization process, be it spinodal decomposition, formation of ''smectic pearls'' or precursor phases followed by local reorganization. This conclusion stems from the analysis of the structure and morphology of polymer single crystals, from the recognition that bulk crystallization leads to similar structures of the lamellae that build up the spherulites, and from the distinctly different structures and morphologies of polymers for which a precursor phase (with either smectic or nematic order) has been recognized. The latter situation, with an intermediate loose pre-order, prevails for polymers with inherent chain rigidity.

Dendritic Crystallization of Poly(l-lactide)/poly(d-lactide) Stereocomplexes in Ultrathin Films

“…23 If PLLA and PDLA in the growth front are imbalanced, the front and the back sides of this growth plane have different (rather than equal) growth rates, and the final single crystal morphology becomes triangular rather than hexagonal. 23,56 Besides the origin of curvatures, the following two phenomena observed in the present study are unexpected and noteworthy:…”

“…Moreover, due to the different chain deposition rates of the two polyenantiomers in nonequimolar PLLA/PDLA blends, the unequal number of PLLA and PDLA chains near the growth tip induces the formation of a unique triangular single crystal in ultrathin films . If PLLA and PDLA in the growth front are imbalanced, the front and the back sides of this growth plane have different (rather than equal) growth rates, and the final single crystal morphology becomes triangular rather than hexagonal. , …”

The influence of short-chain branching on the morphology and structure of polyethylene single crystals

“…All the clues suggest that the interaction of the depositing stem with the growth front is the key factor in the whole crystallization process. For a deeper understanding of lateral crystal habits and polymer crystallization, the reader is referred to important critical reviews regarding the possible processes that determine polymer crystal growth, based mostly on the analysis of the structure and morphology …”

“…For a deeper understanding of lateral crystal habits and polymer crystallization, the reader is referred to important critical reviews regarding the possible processes that determine polymer crystal growth, based mostly on the analysis of the structure and morphology. 31,32 The variations in shape, morphology, and structure of single crystals, particularly of linear PE, have been intensively studied by physicists for more than 50 years. [26][27][28][29][30][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] A renewed interest in the study of linear PE single crystals in the last decade has appeared with the works by Organ et al, 49 Tian et al, 50 Nakamura et al, 51 and Zhang et al 52 However less attention has been paid to the case of branched PE.…”

The structural language of crystalline polymers*

“…In other words, this crystallographic analysis tends to support a step-by step (stem by stem) crystal growth process in polymers that is very similar to the classical picture of the small molecules-type crystal growth. 16,17 III. Crystallization processes: the buildup of a new layer via lateral spread/growth.…”