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The composition and structure of polymer largely determine the properties of its final products. As a novel polymer material, the composition, structure, and properties of the isotactic polypropylene/polybutene-1 in-reactor alloy (iPP/iPB alloy) synthesized by sequential two-stage polymerization with Ziegler-Natta catalyst were correlated for the first time in this work. The iPP/iPB alloy was fractionated by temperature rising elution fractionation (TREF) in a broad temperature ranged from −30 °C to 140 °C, and the chain microstructures and sequence distributions of isolated fractions were analyzed by DSC, GPC, 13C-NMR, and FTIR. The iPP/iPB alloy was composed of five components, namely high isotactic PB (iPB, 85.8 wt%), medium isotactic PB (mPB, 5.1 wt%), poly((butene-1)-block-propylene) copolymers (PB-b-PP, 4.1 wt%) which contained PB and PP blocks with different lengths according to the isolation temperature, isotactic PP (iPP, 2.7 wt%), and atactic PB (aPB, 2.3 wt%). Compared to other commercial pipe materials, the iPP/iPB alloy presented outstanding thermal creep resistance and gas permeability resistance, high strength and low deformation at high temperature, and appropriate flexural strength. The roles of PP and PB-b-PP components in the alloy were interpreted. This work is expected to elucidate the potential application of iPP/iPB alloy as pipe materials and provide solutions for the design and synthesis of high performance pipe materials.

The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl4/MgCl2 Ziegler-Natta (Z-N) catalysts are determined by the structure and nature of active centers, which are mysterious and fairly controversial. In this work, the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene (PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity, active centers with different tacticity and propagation rate constant kp, fragmentation of the catalyst, crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature (60 °C) resulted higher activity, kp and lower [C*], and the isotactic active centers Ci* as the majority ones producing the highest isotactic polypropylene (iPP) components showed much higher kp when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles, and provide the solutions to the improvement of catalyst activity and isotacticity of PP.

For the solid-solid transformation from form II to form I of isotactic polybutene-1 (iPB), the temperature dependence of form I nucleation and growth was deemed to control the transformation process. However, the relationship between form I formation and form II disappearance in the transformation process is not clear. In this work, the spontaneous crystal transformation from form II to I of iPB with 81 mol% mmmm sequence concentration is studied firstly by tracking the two processes, the decay of form II and the yielding of form I in a wide range of temperature spanning from 0 °C to 50 °C and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD. Unlike the literature reports, the decay rate of form II is firstly found to be lower than the yielding rate of form I at all studied temperatures, especially at low transition temperature. This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of form II. The regular chain folding and growth of iPB form I from amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of form I compared with that of initial form II crystallized at 60 °C. An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of iPB form I.

Dingoes are wild canids living in Australia, originating from domestic dogs. They have lived isolated from both the wild and the domestic ancestor, making them a unique model for studying feralization. Here, we sequence the genomes of 10 dingoes and 2 New Guinea Singing Dogs. Phylogenetic and demographic analyses show that dingoes originate from dogs in southern East Asia, which migrated via Island Southeast Asia to reach Australia around 8300 years ago, and subsequently diverged into a genetically distinct population. Selection analysis identifies 50 positively selected genes enriched in digestion and metabolism, indicating a diet change during feralization of dingoes. Thirteen of these genes have shifted allele frequencies compared to dogs but not compared to wolves. Functional assays show that an A-to-G mutation in ARHGEF7 decreases the endogenous expression, suggesting behavioral adaptations related to the transitions in environment. Our results indicate that the feralization of the dingo induced positive selection on genomic regions correlated to neurodevelopment, metabolism and reproduction, in adaptation to a wild environment., Dingoes evolved in isolation from both their domesticated and wild ancestors. Here, the authors investigate the genomic basis of the feralization of dingoes and trace their origin to domestic dogs that migrated to Australia approximately 8300 years ago.

Blending isotactic polybutene-1 (PB) with isotactic polypropylene (PP) is a facial strategy to improve the mechanical properties and promote polymorphous transformation of PB. As the immiscible polymer pairs with strong crystallizability, the interactions between PP and PB in the melt state influence the subsequent processes like phase separation and crystallization, and then determine the crystalline structures and properties of the blends. Herein, two kinds of poly(butene-block-propylene) (PB-b-PP) copolymers with different sequence structures fractionated from PB/PP in-reactor alloy using temperature rising elution fractionation were utilized to compatibilize the PB/PP (80/20) blend. The phase morphologies, crystallization kinetics of PP and PB phases, and crystalline structures in PB/PP/PB-b-PP blends were characterized by phase contrast optical microscopy (PCOM), differential scanning calorimeter (DSC), and small-angle X-ray scattering (SAXS). The PB-b-PP copolymer with longer PP blocks (A) showed more satisfied compatibilization for PB/PP blends and PB/PP/PB-b-PP-2.5 blend with 2.5 wt% copolymer as compatibilizer exhibited the most stable phase morphology with the smallest PP domains in melt state at 200 °C. During isothermal crystallization processes of the PB/PP/PB-b-PP blends at 135 °C for PP crystallization and then 90 °C for PB crystallization, the crystallization rate including nucleation rate and nucleation density, and crystallinity of PP and PB (form II) increased, and achieved the largest when the copolymer concentration was 2.5 wt% in PB/PP/PB-b-PP blend. The copolymer A significantly accelerated crystallization rate of PP compared with that of copolymer B. The PB/PP/A-2.5 blend with the largest lamellae thickness and highest crystallinity of PB form I, combined with the smallest spherulites, exhibited the highest modulus, tensile strength and toughness. The compatibilizing mechanism and roles of PB-b-PP copolymers for PB/PP blends were discussed to understand the physical and mechanical behaviors of the blends.

Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials. In this paper, we addressed the effects of solvent vapor annealing, including chloroform and water vapor, on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1 (PB-1) by means of in situ Fourier transform infrared spectroscopy (FTIR). The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity. Also, a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.

A series of isotactic polybutene-1/polypropylene (PB/PP) in-reactor alloys were prepared by Ziegler-Natta catalyst using sequential two-stage polymerization technology. Temperature rising elution fractionation (TREF) combining with DSC, GPC and 13C-NMR were used to analyze the compositional heterogeneity of the resulting PB/PP alloys. Fractions in the PB/PP alloys, including isotactic polybutene-1, isotactic polypropylene, atactic polybutene-1, a series of copolymers with different length of PB segments, PP segments, and poly(propylene-co-(butene-1)) segments, were isolated for the first time by TREF whereby the chain structure and sequence distribution of these fractions were characterized. A possible mechanism was proposed to explain the fraction formation in this sequential two-stage polymerization technology. The mechanical properties and polymorphic transition of the PB/PP alloys were also studied and correlated with the fraction structure and distribution.