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Samples of isotactic propylene-1-octadecene (iPP-co-C18) random copolymers and of diblock copolymers (BCPs) of isotactic polypropylene (iPP) linked to a propylene-1-octadecene block (P-co-C18), iPP-b-P(P-co-C18) with tuned block length and different comonomer content (up to 24 mol %) have been prepared using two different organometallic Hf-based catalysts. Both catalysts ensure good activity, high comonomer incorporation preserving high molecular weight, and a living behavior with the Cs-symmetric pyridylamido-Hf dimethyl complex. The influence of the copolymer topology with random and block architecture on the crystallization behavior and, specifically, the crystallization of side-chains has been analyzed. In random copolymers iPP-co-C18, the main-chains crystallize in the α form and in a mesophase of iPP, whereas at low temperature, the side-chains of the C18 co-units crystallize forming PE-like crystals. The crystallization of the lateral chains is surprisingly observed even in the sample with low C18 concentration and low branches’ frequency, where the randomly placed branches are highly spaced. This indicates that these random copolymers show unexpected nanophase separation between iPP chains and alkyl side-chains, with aggregation of side-chains that facilitates their crystallization even at low branches’ frequency. In the iPP-b-P(P-co-C18) BCPs, the iPP blocks crystallize in the common α form and the side-chains of the C18 co-units in the P(P-co-C18) block crystallize at low temperature, forming polyethylene-like crystals. The confined crystallization at low temperature of side-chains of the C18 co-units is driven by both phase separation of the dissimilar blocks (further driven by iPP crystallization) as well as by phase separation induced by the local incompatibility inside the P(P-co-C18) block between main-chain and C18 side-chains. This cooperative mechanism further facilitates the crystallization of the C18 side-chains compared to random copolymers and provides indirect evidence of microphase separation in these systems. We have demonstrated that branches are intriguingly segregated in nanodomains, favoring crystallization after self-aggregation, and can crystallize in random copolymers with a perfectly uniform and random distribution of C18 co-units even at very low comonomer content, therefore, even for low frequency of branching, when randomly placed branches are highly spaced.

Crystalline–amorphous diblock copolymers (BCPs) comprising crystalline blocks of isotactic polypropylene (iPP) or polyethylene (PE) linked to amorphous blocks of random ethylene–propylene copolymers (EPR) (iPP-b-EPR and PE-b-EPR) of different block lengths and ethylene concentrations in EPR blocks, and crystalline–crystalline BCPs composed by iPP and PE blocks (iPP-b-PE) have been synthesized with different living catalysts. The effects of the presence of a linked EPR rubbery block of varying composition on the crystallization behaviors and kinetics of PE and iPP, and of crystalline PE or iPP block on the crystallization kinetics of linked iPP or PE, respectively, have been analyzed. All samples have been isothermally crystallized from melting at different temperatures, and the crystallization kinetics have been analyzed. In iPP-b-PE BCPs, the PE block crystallizes first from the melt during nonisothermal cooling or isothermal crystallization. The iPP block crystallizes after PE and nucleates over the PE crystals. In both iPP-b-EPR and PE-b-EPR BCPs, the linked amorphous EPR block slows down the crystallization of iPP and PE blocks with respect to their respective homopolymers. Furthermore, in iPP-b-EPR samples, a higher concentration of propylene in the EPR phase results in a more significant slowdown of the crystallization kinetics of iPP due to a higher solubility between the blocks. Analogously, in PE-b-EPR copolymers, the increase in the length of the EPR block results in a more pronounced slowdown of the crystallization rate of PE with respect to the PE homopolymer due to the significant dilution exerted by the long EPR block. All samples of iPP-b-PE copolymers show crystallization rates lower than that of the PE homopolymer but faster than that of the iPP homopolymer. In isothermal crystallization experiments, the iPP blocks do not crystallize, not even at low crystallization temperatures, but crystallize upon successive cooling, nucleating over the PE crystals formed in the isothermal step. Therefore, the linked iPP, which remains in the melt during the isothermal crystallization, slows down the crystallization kinetics of PE, in contrast to what happens in a sample of iPP/PE blend, where the crystallization kinetics of PE is not affected by the presence of the phase-separated iPP.