Structure Of Copolymers Research Articles

Grafting modification of poly(vinylidene fluoride-hexafluoropropylene) via Cu(0) mediated controlled radical polymerization

In the present work, diverse vinyl monomers were successfully grafted onto poly(vinylidene fluoride-hexafluoropropylene) P(VDF-HFP) via direct activation of CF bonds using Cu(0)/4,4′-dimethyl-2,2′-bipyridyl (DMDP) as catalyst under mild conditions. The structure of the graft copolymer was carefully characterized, and the initiating site was confirmed at the same time. Moreover, the kinetic results indicated the controlled behavior of the graft polymerization, and the composition of the graft copolymer can be regulated by changing the reaction conditions. This work may provide a facile strategy to endow P(VDF-HFP) copolymer with new functions via directly activating CF bonds.

Ceric-ions redox initiating technique for Zirconium and Niobium separation through graft copolymerization of natural polysaccharides

ABSTRACT The modification of the polysaccharides as a significant route to alter the physical and chemical properties via Ceric-initiated graft copolymerization of Acrylonitrile (AN) onto Carboxymethyl cellulose (CMC) was performed under inert atmosphere using ceric ammonium nitrate (CAN) as an initiator to prepare CMC-g-PAN copolymers. In this respect, NaOH solution hydrolyzed the graft copolymer, CMC-g-PAN, to obtain hydrolyzed CMC-g-PAN hydrogel, in which the CMC-g-PAN nitrile groups were totally transformed into a combination of hydrophilic carboxamide and carboxylate groups (H-CMC-g-PAN). Pure CMC and grafted copolymers structure were identified by an analyzation of FTIR spectral data, TGA, SEM and XRD. These biodegradable and low-cost graft copolymers, with improved features could really be utilized as promising adsorbents for separation and recovery of some metal values from different media. H-CMC-g-PAN was implanted for the effective separation of Zr(IV) and Nb(V) from nitric acid solution and the batch experimental results indicate that the extraction percentage by adsorbent gradually decreased by raising the HNO3 molarity. The calculated maximum capacity of H-CMC-g-PAN is 10.56 mg.g−1 Zr(IV) and 14.07 mg.g−1 Nb(V) under the used experimental conditions. Desorption investigation shows that the maximum desorption of Zr(IV) and Nb(V) was achieved with 1 M HCl, while selective stripping of Niobium was carried out using 1 M sodium hydroxide.

Bridging from the Sequence to Architecture: Graft Copolymers Engineering via Successive Latent Monomer and Grafting‐from Strategies†

Main observation and conclusionThe on‐demand building copolymer structures, from sequence to architecture, is crucial in understanding the relation between polymer structure and property, meanwhile motivating the innovation of polymer hierarchy. However, the challenge is conspicuous for complicated polymer structures from inherently intricate polymerization. In this work, copolymers with tailored grafting density and distributions were achieved using successive latent monomer and grafting‐from strategies. The hydroxyl group functionalized furan/maleimide adduct (FMOH) was selected as the latent monomer for RAFT polymerization of an array of copolymers with tailored localization of hydroxyl group along the main chain. The hydroxyl group further initiated the ring opening polymerization (ROP) of L‐lactide or ε‐caprolactone, resulting in a library of multicomponent copolymers via grafting‐from strategy. The initiating efficiency reached to ~100% with variable molecular weight (21300—58600 Da) and narrow distributions (ÐM < 1.25), indicating that such graft copolymers possessed controlled density and distribution of side chains as its linear template. The investigation on thermal properties of the well‐defined graft copolymers implied that the precise tailoring over copolymer structures at the molecule level could lead to tunable chemical/physical properties. This work bridged polymer from sequence to architecture, unveiled a new method in creating graft copolymers with programmable structures and provided the insight into the structure/property relationship.

Morphological evolution of self‐assembled PS‐g‐PA6 graft copolymer via in situ polymerization

AbstractThe self‐assembly behaviors of polystyrene graft polyamide‐6 (PS‐g‐PA6) copolymer obtained through incorporation of PA6 and PS segments with exact lengths via in situ polymerization were studied in this work. Copolymers were obtained via the bulk polymerization induced self‐assembly process without any external template or stabilizer. The morphological characteristics of PS‐g‐PA6 copolymer were probed using SEM and TEM techniques. Particular attention was paid to changing the PS‐g‐PA6 morphology from a simple nanospherical to the combined nano/microspherical phase structure by varying the [PA6]/[PS] mass ratio. At a [PA6]/[PS] mass ratio of 80:20, PS‐g‐PA6 copolymer revealed a specific phase structure, where the PS backbones formed a continuous phase and the PA6 side chains ensured the microspheres with dispersed nano‐scale inclusions. The grain diameter of a dispersed PA6 sphere phase was found to be about 75 nm. When the PS backbone mass ratio decreased to 10 wt%, the copolymer structure was self‐assembled into the 1–3 μm large microspheres with uniformly distributed nanospherical particles. A further decrease in the PS backbone content to 5 wt% led to the failure of phase inversion in the copolymers. The main feature of this project is that the structure of the main chain and branch chain of PS‐g‐PA6 copolymer can be reversed. The branched chain forms spherical phase and the main chain forms continuous phase structure. The strategy was proved to be effective to obtain the novel structure of graft copolymer.

Effect of Dexamethasone on Thermoresponsive Behavior of Poly(2-Oxazoline) Diblock Copolymers.

Thermoresponsive polymers play an important role in designing drug delivery systems for biomedical applications. In this contribution, the effect of encapsulated hydrophobic drug dexamethasone on thermoresponsive behavior of diblock copolymers was studied. A small series of diblock copoly(2-oxazoline)s was prepared by combining thermoresponsive 2-n-propyl-2-oxazoline (nPrOx) and hydrophilic 2-methyl-2-oxazoline (MeOx) in two ratios and two polymer chain lengths. The addition of dexamethasone affected the thermoresponsive behavior of one of the copolymers, nPrOx20-MeOx180, in the aqueous medium by shifting the cloud point temperature to lower values. In addition, the formation of microparticles containing dexamethasone was observed during the heating of the samples. The morphology and number of microparticles were affected by the structure and concentration of copolymer, the drug concentration, and the temperature. The crystalline nature of formed microparticles was confirmed by polarized light microscopy, confocal Raman microscopy, and wide-angle X-ray scattering. The results demonstrate the importance of studying drug/polymer interactions for the future development of thermoresponsive drug carriers.

Structural and Thermal Studies of Fluorescein and Rhodamin6G Grafted Diblock Copolymers

The ring-opening polymerization (ROP) of tetrahydrofuran (THF) and ε-caprolactone (CL) was performed at 160 °C for 2 h under N2 ambiance using two different dyes such as fluorescein (Flur) and rhodamin6G (R6G) as a novel initiator. The structure of the dye-centered diblock copolymers was confirmed by analyzing the NMR spectra. The melt transition temperature and thermal stability of the polymers were determined by DSC and TGA. The FT-IR spectra indicated the functional groups present in the dye grafted homopolymer and diblock copolymers. The increase in molecular weight (Mw) of the dye-centered diblock copolymer was confirmed by the GPC measurement. The conjugation of dye with the polymer backbone was carried out by a single-step method without using any hazardous solvents.

Flow-induced crystallization of a multiblock copolymer under large amplitude oscillatory shear: Experiments and modeling

Following a previous work investigating the flow-induced crystallization (FIC) of polybutylene terephthalate/polytetrahydrofuran (PBT/PTHF) multiblock copolymers under steady shear, we propose here to deal with the case of large amplitude oscillatory shear (LAOS). For this purpose, we focus on a single copolymer (Mw¯=50kgmol−1) made, in average, of a sequence of nine soft and eight hard segments. We show unambiguously that LAOS accelerates the polymer crystallization when increasing (i) the frequency from 0.5 up to 50 rad s−1 (at a constant strain amplitude of 100%) or (ii) the strain amplitude from 10 to 300% (at a constant frequency of 2.5 rad s−1). Based on this data, we demonstrate that high oscillatory shear rates have similar effects as the steady shear rate regarding the gelation time, i.e., that frequency- and strain amplitude-related effects are secondary. We carefully analyze the stress response through Fourier-transform decomposition that emphasizes the rich rheological behavior of our material during its liquid-to-solid phase transition. With the help of x-ray scattering experiments (ex situ SAXS and WAXS), we then propose a global scenario rationalizing the whole set of rheological observations based on the copolymer structure. In parallel, we propose to use a recent model that we developed to simulate the stress response in the case of steady shear-promoted FIC and adapt it to the case of LAOS. Remarkably, our model, which is based on modified Doi–Edwards equations only, provides good qualitative agreement with the data when varying the strain amplitude or the frequency. Furthermore, it is found to predict quantitatively the gelation time of the system.

Structure of Diisobutylene Maleic Acid Copolymer (DIBMA) and Its Lipid Particle as a "Stealth" Membrane-Mimetic for Membrane Protein Research.

The study of membrane proteins remains challenging, especially in a native membrane environment. Recently, major progress has been made using maleic acid copolymers, such as styrene maleic acid, to purify membrane proteins and study them directly with native lipids associated with the membrane. Additional maleic acid copolymers, such as diisobutylene maleic acid (DIBMA) membrane-mimetic systems, are being developed and found to have improved spectroscopic properties and pH stability. We studied DIBMA and its lipid particles in solution to better understand its assembly, without and with the lipids, to provide an insight regarding how to use it in solution for better membrane extraction. Using small-angle neutron and X-ray scattering (SANS/SAXS), we show that DIBMA organizes into structures of different size scales at various concentrations and ionic strengths. The polymer performed reasonably well under most solvent conditions except in very low concentrations and high-salt conditions that could result in limited interaction with lipids. To explore DIBMA lipid particles as a suitable membrane-mimetic system for neutron scattering studies of membrane proteins, we measured and determined the contrast-matching point of DIBMA to be ∼12% (v/v) D2O - similar to that of most protiated lipid molecules but distinct from that of regular protiated proteins - providing a natural contrast for separating their neutron scattering signals. Using SANS contrast variation, we demonstrated that the scattering from the whole lipid particle can be annihilated. Further, we determined that a well-defined lipid nanodisc structure with DIBMA was contrast-matched. These results demonstrate that the DIBMA lipid particle is an outstanding "stealth" membrane-mimetic for membrane proteins. The results provide a structural framework for understanding the organization and assembly process of the polymer itself and the lipid molecules. Such an understanding is imperative for structural techniques such as cryo-electron microscopy, nuclear magnetic resonance, small-angle scattering, and other biophysical techniques.

Molecular dynamics simulation based design of biomimetic membrane with artificial water channels

Inspired by nature’s design of pore proteins embedded in cell membranes, synthetic pore molecules embedded in self-assembled amphiphilic block copolymer membranes are the subject of intensive current research, as a possible route to more efficient reverse osmosis (RO) membranes. RO membranes are the key element in producing drinkable water from brackish or sea water; improved materials would help make this expensive process more widely applicable, increasing fresh water supplies worldwide. In this work, we simulated polybutadiene–polyethylene oxide (PB–PEO) bilayers containing peptide-appended pillar[5]arene (PAP5) channels. PB–PEO bilayers with PAP5 channels are a biomimetic alternative to aquaporin embedded lipid membranes, with high water permeability combined with excellent selectivity. In our simulations, we systematically varied the PB–PEO block copolymer structure to maximize water mobility. We measured water diffusivity in our best design by two complementary methods, and compared our values to that inferred from experimental channel permeability. In this design, we obtained a water diffusivity of 30.38 ± 0.19 × 10−8cm2s−1, comparable to the best experimentally reported result. We find that the highest permeability is achieved when the bilayer hydrophobic thickness matches the PAP[5] dimension, and the hydrophilic block is long enough that clogging the pore is entropically unlikely.

Tunable plasticization of sustainable ethyl cellulose toward thermoplastic elastomers through ATRP grafting

Thermoplastic elastomers (TPEs) derived from sustainable cellulose and its derivatives have attracted a great deal of attention, because of their abundance, renewable nature, rigid backbone and good mechanical properties. To fabricate TPEs with tunable performance, a series of sustainable ethyl cellulose (EC)-grafted poly(methyl methacrylate (MMA)) (EC-g-P(MMA)) and poly(MMA-co-butyl methacrylate (BMA)) (EC-g-P(MMA-co-BMA)) were fabricated by way of atom-transfer radical polymerization (ATRP). By tuning the molar ratio of MMA/BMA in the copolymer side chains, tunable performance of TPEs with tunable glass transition temperatures (118–47.8°C) was achieved. The chemical structures of EC-bromide and EC graft copolymers were identifiable by Fourier transform infrared spectroscopy and hydrogen-1 (1H) nuclear magnetic resonance spectroscopy. The EC graft copolymers exhibited a higher molecular weight and good thermal stability and mechanical properties. These results suggested that these tunable-performance copolymers with a sustainable cellulose backbone and an acrylate side chain were potential candidates for service as TPEs in some applications.

Molecular Structure of Gardenia Blue Pigments by Reaction of Genipin with Benzylamine and Amino Acids.

Genipin was reacted with benzylamine and several amino acids to prepare gardenia blue (GB). The time-course of GB formation with benzylamine was monitored by high-performance liquid chromatography (HPLC), liquid chromatography time-of-flight mass spectrometry (LC-TOFMS), and 1H and 13C NMR measurements. In this experiment, we determined the molecular structures of some intermediates using accurate masses and additional NMR techniques such as heteronuclear multiple bond correlation (HMBC). GBs with amino acids (GB-AAs) were characterized by both liquid and solid-state NMR measurements. Interestingly, many significant peaks appeared in the solid-state NMR spectra, although the 13C NMR spectra from solution samples did not show any distinct peaks. Therefore, we determined that GB-AAs had an alternating copolymer structure composed of methyne and 5H-2-pyrindine, which was substituted by amino acids at N atom and linked with methyne at 5 and 7 positions. To confirm this molecular structure, the pyrolysis gas chromatography-mass spectrometry (GC-MS) measurement of GB-AAs was carried out, and 5H-2-pyrindine and its methyl derivatives were formed as main pyrolysis products from the polymer chains.

Allostery‐Mimicking Self‐assembly of Helical Poly(phenylacetylene) Block Copolymers and the Chirality Transfer

AbstractAllostery can regulate protein self‐assembly which further affects biological activities, and achieving precise control over the chiral suprastructures during self‐assembly remains challenging. Herein, to mimic the allosterical nature of proteins, the poly(phenylacetylene) block copolymers PPA‐b‐PsmNap with the dynamic helical backbone were synthesized to investigate their conformational‐transition‐induced self‐assembly. As the helical conformation of the block PsmNap spontaneously transforms from cis‐transiod to cis‐cisoid, the decreasing solubility of PsmNap blocks in THF induced self‐assembly of PPA‐b‐PsmNap. The self‐assembly structures of copolymers can sequentially evolve from vesicles to nanobelts to helical strands during the process of conformation transformation. The screw sense of final helical strands was strictly correlated to the helicity of the block PsmNap. This is helpful to understand the mechanism of allostery‐modulated self‐assembly.

A Novel Polymer Insect Repellent Conjugate for Extended Release and Decreased Skin Permeation of Para-Menthane-3,8-Diol.

Background: We developed a novel polymer insect repellent conjugate for extended release and decreased skin permeation of the volatile insect repellent p-menthane-3,8-diol (PMD). Methods: PMD was conjugated with acryloyl chloride via an ester bond to form acryloyl–PMD, which was subsequently copolymerised with acrylic acid at varying molar ratios. Copolymer structures were characterised by 1H NMR and FT-IR, analysed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), molecular weights and reactivity ratios determined, and repellent loading assessed. Results: Using porcine liver esterases, ~45% of the insect repellent was released over five days. Penetration and permeation studies of the copolymer and free repellent using excised, full-thickness porcine ear skin showed no detectable permeation of the copolymer through skin compared to the PMD. Moreover, tape stripping revealed that over 90% of the copolymer remained on the outer surface of the skin, whereas free PMD was within all skin layers. A planarian toxicity fluorescence assay indicated that that the copolymer is unlikely to be a significant irritant when applied topically. Conclusions: this study demonstrates the feasibility of the copolymer approach to develop extended-release insect repellents while reducing skin uptake and transdermal permeation of the small-molecular-weight active ingredient, in order to minimise any adverse effects.

Allostery-Mimicking Self-assembly of Helical Poly(phenylacetylene) Block Copolymers and the Chirality Transfer.

Allostery can regulate protein self-assembly which further affects biological activities, and achieving precise control over the chiral suprastructures during self-assembly remains challenging. Herein, to mimic the allosterical nature of proteins, the poly(phenylacetylene) block copolymers PPA-b-PsmNap with the dynamic helical backbone were synthesized to investigate their conformational-transition-induced self-assembly. As the helical conformation of the block PsmNap spontaneously transforms from cis-transiod to cis-cisoid, the decreasing solubility of PsmNap blocks in THF induced self-assembly of PPA-b-PsmNap. The self-assembly structures of copolymers can sequentially evolve from vesicles to nanobelts to helical strands during the process of conformation transformation. The screw sense of final helical strands was strictly correlated to the helicity of the block PsmNap. This is helpful to understand the mechanism of allostery-modulated self-assembly.

Flame retardance enhancement of polyacrylonitrile with dimethyl vinylphosphonate

AbstractTo obtain a polyacrylonitrile (PAN) material with highly thermal stability and flame retardance properties, a novel P(AN‐co‐DMVP) copolymers were successfully synthesized by randomly copolymerization. According to thermogravimetry analysis, it revealed that incorporating dimethyl vinylphosphonate (DMVP) into the PAN chains can perform outstanding thermal stability. Furthermore, the limiting oxygen index increased from 18.6% to 30.0% with addition of 22.6 wt% DMVP. The results of cone calorimetry tests certified that the peak‐heat release peak and total heat release of P(AN‐co‐DMVP22.6) were remarkably dropped by 70% and 33%, respectively, suggesting excellent flame retardance. The relationship between copolymer structures and flame‐retardant performance was systematically investigated by X‐ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis‐Fourier transform infrared and Pyrolysis gas chromatography/mass spectrometry. A comprehensive flame‐retardant mechanism has been proposed that DMVP plays a role in both the gaseous phase and the condensed phase.

Combining Renewable Ethyl Cellulose and Acrylate to Fabricate Sustainable TPEs via Controlled Polymerization

A series of ethyl cellulose (EC) grafted copolymers were fabricated with methyl methacrylate (MMA), stearyl methacrylate (SMA) and EC grafted 2-bromoisobutyryl bromide(EC-Br) as macroinitiator via atom transfer radical polymerization (ATRP). The chemical structures of EC-Br and EC graft copolymers were identified by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR) spectroscopy. The EC graft copolymers exhibited higher molecular weight and polydispersity index value. With the dosage of SMA increased, EC grafted copolymers exhibited glass transition temperatures in a broad temperature range from 119.1 to 42.3 ℃. And the initial decomposition temperature (Ti) of EC grafted copolymers were increased (148.2 ℃ to 199.4 ℃). The stresses at break of EC grafted copolymers were decreased with the increase of SMA content. However, the elongation at break of all EC grafted copolymers were increased with the dosage of MMA decreased. These results suggested that the sustainable copolymers with cellulose backbone, acrylate side-chain were potential candidates for service as TPEs in some applications.

Free volume characteristics of 2,2‐bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene copolymers: Effect of composition and molecular weight

Abstract2,2‐bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene (PDD‐TFE) copolymer is a good candidate to prepare gas separation membranes with excellent permeability due to its free volume characteristics. However, the influence of PDD‐TFE copolymer structure on its free volume characteristics is less studied. In this paper, PDD‐TFE copolymers with different compositions and molecular weights were synthesized, and their free volume characteristics were analyzed by positron annihilation lifetime spectroscopy and a molecular dynamics simulation. It indicated that the molar fraction of PDD in copolymers had a significant effect on free volume characteristics, while the molecular weight of copolymers exerted a slight influence on free volume when the molecular weight exceeded a critical region (intrinsic viscosity [η] > 68 ml g−1). PDD‐TFE copolymers with greater PDD molar fractions (i.e., 72% and 84%) showed bimodal distributions in positron lifetime and free volume size distributions, while PDD‐TFE copolymers with lower PDD molar fractions (i.e., 27% and 35%) exhibited a single peak. The long‐lifetime parameter τ3 was assigned to micro‐cavities formed by [‐(TFE)y‐PDD‐] segments and τ4 was attributed to micro‐cavities formed by [‐(PDD)x‐TFE‐] segments. The cis and trans transitions of PDD led to a local multilayer spiral structure with a 2.6–4.3 Å layer spacing, which would also increase the free volume of copolymers.

Hierarchical Self‐Assembly of Polyethylene Midblock Copolymers in Hot Steam: Key Role of Crystalline and Topological Structure

AbstractA series of linear‐shaped, H‐shaped, and dumbbell‐shaped semi‐crystalline triblock copolymers (E1, E2 and E3) is prepared, which contains polyethylene (PE) midblock and poly(methyl methacrylate) (PMMA) endblocks. The molecular design in this study is focused on the variation of the length and number of PMMA chains, with a fixed PE midblock (Mn = 16 000 g mol−1) and approximate composition (wtPE%:wtPMMA ≈ 1:1), upon which the hierarchical self‐assembly behavior in solvent vapor annealing (SVA) process is investigated. The dumbbell‐shaped E3, which contains the most and shortest PMMA chains, shows a drastic reduction of the Tm and crystallinity of PE midblock. It is attributed to the plasticization effects by the dumbbell architecture, which disturbed the chain folding of PE block. The variation of the topological structure of copolymers not only accelerates the transformation of morphologies from spherical to network, but also leads to the formation of new morphologies. After repeated annealing, both E1 and E2 form crossed network, columnar and flower‐like morphologies by higher‐level assembly from preassembled vermicular micelles. By comparison, the dumbbell‐shaped E3 assembled into lamellar or stacks of “lamellar” morphologies. The hierarchical self‐assembly can be governed by the combination of the driving forces of PE crystallization and the topologies structure.

Separation of phenyl acetic acid and 6-aminopenicillanic acid applying aqueous two-phase systems based on copolymers and salts

6-Aminopenicillanic acid (6-APA) is used for synthesis of semisynthetic antibiotics. Polymer-salt aqueous two-phase systems (ATPSs) were applied for separation of 6-APA and phenyl acetic acid (PAA), as the products of hydrolyzation reaction of Penicillin G/Penicillin V. The binodal curves of ATPS composed of a copolymer (reverse Pluronic 10R5, Pluronic L35 and PEG-ran-PPG) and a salt (Tri-sodium citrate, tri-potassium citrate, di-potassium phosphate, sodium sulphate and magnesium sulphate) were obtained. The results show that, at a fixed PPG/PEG ratio, block copolymers have larger two-phase region compared with random copolymer. After screening on the partition coefficient of PAA and 6-APA separately, Na2SO4 was selected for studying the effect of the copolymer structure and the composition of salt and copolymer on partitioning, considering higher selectivity of PAA and 6-APA. 10R5-Na2SO4 ATPS was selected as the most appropriate system for separation of 6-APA and PAA. This system was used for separation of mixture of 6-APA and PAA. The results show that selectivity was approx 53 and smaller in a system, containing a mixture of 6-APA and PAA. This observation can be justified by the interaction between 6-APA and PAA. Molecular interaction between these two molecules were investigated by the Flory–Huggins interaction parameter.

Mesostructure of Composite Materials Based on Segmented Poly(Urethane Imide) Containing Ferrite Nanoparticles

The mesostructure of segmented poly(urethane imide) containing 4–10 wt % CoFe2O4 or Al3Fe5O12 nanoparticles was experimentally studied by small-angle polarized neutron scattering, which can analyze the nuclear and magnetic subsystems of the obtained composites. The transformation of the domain structure of the magnetic elastomers based on poly(urethane imide) was investigated at various concentrations, chemical compositions, and localizations of ferrite nanoparticles in polymer chains. The dynamics of the change in the segmental mobility of soft blocks during heating of samples was characterized by magnetic–nuclear interference scattering. The experiments detected changes in the supramolecular structure of the multiblock copolymer, which depended on the percentage and type of nanoparticles. The correlation radii were determined in the magnetic subsystem of ferrite nanoparticles embedded in hard aromatic blocks of poly(urethane imide) as nodes of intermolecular crosslinkers and chain extenders. The temperature dependence was analyzed for the intensity of small-angle nuclear scattering by poly(urethane imide) and magnetic elastomers based on it, under the conditions of the transition of soft aliphatic segments from the glassy to the highly elastic state.