An isochronous decoration method for measuring linear growth rates in polymer crystals

The long spacing l of lamellar crystals of linear polyethylene increases with the crystallization temperature T_c. For low degrees of supercooling, the ratio Δl/ΔT is around 0.5 nm K^?1 for PE single crystals obtained from solution in xylene. In the restricted situation where only conduction in the crystallization vessel is involved, a heat transfer analysis shows that about 20 s is needed to change by 5 K the crystallization temperature T_c in a cylindrical vessel of 1.5 mm radius. Such rapid change of the crystallization temperature induces a sharp increase or decrease of the thickness of the single crystals. After conventional shadowing with palladium–gold alloy, the steps on the crystals are observed by conventional bright-field electron microscopy. A pioneering work was performed in this way by Bassett and Keller in 1962. Our technique allows one to determine both the shape and the dimensions of single crystals or twinned crystals of polyethylene as a function of the time of crystallization, and therefore give the quasi-instantaneous growth rates at various times.     

Degradation on freezing dilute polystyrene solutions in p-xylene

Chain scission was observed during the crystallization of p-xylene in dilute polystyrene solutions. Degradation yields were determined by gel permeation chromatography, as a function of the number of freeze-and-thaw cycles, polymer concentration, and initial polymer molecular weight (M). The rate constant for chain scission K_c increases with the polymer chain length, from 0.021%/cycle at M = 110·10³ to 4.7%/cycle at M = 8.5·10⁶. Over the two decades range of investigated molecular weights, K_c follows an empirical scaling law of the form K_c ～ (M ? M_lim)^1.17578, where M_lim is a limiting molecular weight ? 29,000 g. mol^?1 below which no degradation could be induced. Some propensity for midchain scission was detected, although this tendency was much weaker in comparison to flow-induced degradation. A chain scission model based on crack propagation failed to reproduce the experimental results. To explain the observed dependence of K_c with the square of the radius of gyration, an interfacial stress transmission mechanism between the crystallization fronts and the polymer coil has been proposed. © 1994 John Wiley & Sons, Inc.     

Studies of non-isothermal crystallization and melting of ultra high molecular weight polyethylene

The non-isothermal crystallization and melting of ultra high molecular weight polyethylene (UHMWPE) were observed by means of differential scanning calorimetry and compared with those of ordinary high-density polyethylene (HDPE). The crystallization temperature (T _c ) and melting point (T _m ) of UHMWPE were found to be higher thanT _c andT _m of HDPE, and the latent heat of crystallization (δH _c ) and fusion (δH _m ) of UHMWPE are smaller thanδH _c andδH _m of HDPE. The results were explained in terms of the theory of polymer crystallization and the structure characteristics of UHMWPE. The relationships between the parameters (T _c ,T _T ,δH _c andδH _m ) and the molecular weight (M) of UHMWPE are discussed. Processing of the experimental data led to the establishment of four expressions describing the above relationships.     

Observation of Regime III Crystallization in Polyethylene/Montmorillonite Nanocomposites

Summary: Exfoliated and intercalated polyethylene/montmorillonite (PE/MMT) nanocomposites with high MMT content were prepared by in situ polymerization. The isothermal crystallization kinetics of the nanocomposites were analyzed with Lauritzen–Hoffman regime theory. Regime III crystallization, which is difficult to observe in linear polyethylene, appears in the PE/MMT nanocomposites. The broader temperature range of regime III crystallization in PE/MMT nanocomposites shows that the mobility and reptation ability of the PE chains are greatly reduced by the MMT, especially in the intercalated nanocomposite.

Plots of ln K/n + U*/R(T_c − T₀) against 1/T_c(ΔT)f for the intercalated and exfoliated PE/MMT nanocomposites.     

Oligonucleotide Analogues with Integrated Bases and Backbone. Part 16

The self‐complementary, ethylene‐linked U*[c_a]A⁽*⁾ dinucleotide analogues 8, 10, 12, 14, 16 , and 18 , and the sequence‐isomeric A*[c_a]U⁽*⁾ analogues 20, 22, 24, 26, 28 , and 30 were obtained by Pd/C‐catalyzed hydrogenation of the corresponding, known ethynylene‐linked dimers. The association of the ethylene‐linked dimers was investigated by NMR and CD spectroscopy. The U*[c_a]A⁽*⁾ dimers form linear duplexes and higher associates (K between 29 and 114M ^?1). The A*[c_a]U⁽*⁾ dimers, while associating more strongly (K between 88 and 345M ^?1), lead mostly to linear duplexes and higher associates; they form only minor amounts of cyclic duplexes. The enthalpy–entropy compensation characterizing the association of the U*[c_x]A⁽*⁾ and A*[c_x]U⁽*⁾ dimers (x=y, e, and a) is discussed.     

Synthesis and characterization of well‐defined cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s and amphiphilic star poly(ε‐caprolactone‐b‐ethylene glycol)s

Per‐2,3‐acetyl‐β‐cyclodextrin with seven primary hydroxyl groups was synthesized by selective modification and used as multifunctional initiator for the ring‐opening polymerization of ε‐caprolactone (CL). Well‐defined β‐cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s (CDSPCLs) with narrow molecular weight distributions (≤1.15) have been successfully prepared in the presence of Sn(Oct)₂ at 120 °C. The molecular weight of CDSPCLs was characterized by end group ¹H NMR analyses and size‐exclusion chromatography (SEC), which could be well controlled by the molar ratio of the monomer to the initiator. Furthermore, amphiphilic seven‐arm star poly(ε‐caprolactone‐b‐ethylene glycol)s (CDSPCL‐b‐PEGs) were synthesized by the coupling reaction of CDSPCLs with carboxyl‐terminated mPEGs. ¹H NMR and SEC analyses confirmed the expected star block structures. Differential scanning calorimetry analyses suggested that the melting temperature (T_m), the crystallization temperature (T_c), and the crystallinity degree (X_c) of CDSPCLs all increased with the increasing of the molecular weight, and were lower than that of the linear poly(ε‐caprolactone). As for CDSPCL‐b‐PEGs, the T_c and T_m of the PCL blocks were significantly influenced by the PEG segments in the copolymers. Moreover, these amphiphilic star block copolymers could self‐assemble into spherical micelles with the particle size ranging from 10 to 40 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6455–6465, 2008     

Matched ring diblock and linear triblock copolymers in dilute solution

A unique diblock copolymer ring and its linear triblock copolymer precursor composed of polystyrene and polydimethylsiloxane have been characterized by static and dynamic light scattering in dilute solution. The measurements were carried out with cyclohexane as the solvent over a temperature range of 12–35°C. Cyclohexane has the useful property that it is nearly isorefractive with the PDMS so that the PDMS block segments are invisible to the light-scattering technique and it is a theta solvent for polystyrene at 34.5°C. The block polymers in this work contain 35.1 wt % of styrene as determined by proton NMR. In the linear triblock polymer, the polystyrene is the center block with PDMS blocks on each side. Static light scattering measurements give 4.31 × 10⁴ for the average molecular weight of the whole polymer. Light scattering also shows that the apparent theta temperature for the linear triblock is shifted by 15°C to a value of 20°C at which point the second virial coefficient drops sharply and phase separation begins to induce aggregation. The diblock ring, however, shows a strongly positive second virial coefficient and no aggregation even at 12°C which is the limit of these experiments. The diffusion coefficients of cyclic diblock (D_c) and linear triblock copolymer (D₁) are measured by dynamic light scattering. The ratio of diffusion coefficients of cyclic and linear copolymers at 14.9°C and 30°C are D_c/D_l = 1.13 and 1.107 respectively. These compare well with prediction of 1.18 for this ratio from consideration of the hydrodynamics of matched linear and cyclic polymer chains. Dynamic light scattering quantitatively confirms that the linear copolymer experiences a solvent quality change near 20°C but the cyclic polymer remains in good solvent over the entire experimental temperature range. © 1993 John Wiley & Sons, Inc.     

One-pot orthogonal thiol-ene click polymerization and ring-opening grafting reaction of CO2-based disubstituted δ-valerolactone

Being a disubstituted δ-valerolactone synthesized by the telomerization of carbon dioxide with 1,3-butadiene, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL) contains a six-membered ring and two unsaturated groups. This report describes the synthesis of an amphiphilic graft copolymer by the combination of thiol-ene click polymerization and ring-opening grafting reaction of EVL, ethyldithiol (EDT), and methoxy polyethylene glycol (mPEG-OH). The alternating copolymer of P(EVL-alt-EDT) with 17.9 wt% CO₂ content and weight-average molecular weight (M_w) of 7 kg/mol was prepared by means of the free radical thiol-ene click polymerization of EVL with EDT initiated by 2,2-dimethoxy-1,2-diphenylethanone under UV irradiation. The following alcoholysis of the lactone ring of P(EVL-alt-EDT) backbone by mPEG-OH is catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene, producing the amphiphilic graft copolymer P(EVL-alt-EDT)-g-PEG₇₅₀ with M_w of 12 kg/mol. The polymers are characterized by nuclear magnetic resonance, Fourier transform infrared, matrix-assisted laser desorption ionization-time of flight mass spectra, size exclusion chromatography and differential scanning calorimetry. The one-pot orthogonal strategy is a new utilization of EVL in synthetic polymers and it is significant to the carbon dioxide transformation.     

Synthesis,crystallization kinetics,and spherulitic growth of linear and star‐shaped poly(L‐lactide)s with different numbers of arms

Well‐defined linear poly(L ‐lactide)s with one or two arms (LPLLA and 2LPLLA, respectively) and star‐shaped poly(L ‐lactide)s with four or six arms (4sPLLA and 6sPLLA, respectively) were synthesized and then used for the investigation of the thermal properties, isothermal crystallization kinetics, and spherulitic growth. The maximal melting temperature, the cold‐crystallization temperature, and the degree of crystallinity of these poly(L ‐lactide) polymers decreased with an increasing number of arms in the macromolecule. Moreover, the isothermal crystallization rate constant (K) of these poly(L ‐lactide) polymers decreased in the order of K_LPLLA > K_2LPLLA > K_4sPLLA > K_6sPLLA2, which was consistent with the variation trend of the spherulitic growth rate (G). Meanwhile, both K and G of 6sPLLA slightly increased with the increasing molecular weight of the polymer. Furthermore, both LPLLA and 2LPLLA presented spherulites with good morphology and apparent Maltese cross patterns, whereas both unclear Maltese cross patterns and imperfect crystallization were observed for the star‐shaped 4sPLLA and 6sPLLA polymers. These results indicated that both the macromolecular architecture and the molecular weight of the polymer controlled K, G, and the spherulitic morphology of these poly(L ‐lactide) polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2226–2236, 2006     

The effect of molecular weight on the crystallization kinetics and equilibrium melting temperature of poly(tetramethylene ether glycol)

Isothermal crystallization of poly(tetramethylene ether glycol) (PTMEG) with relatively low molecular weight (M_n = 991, 2004 and 2864, respectively) was investigated by differential scanning calorimetry, and the equilibrium melting temperature (T) determined using the Hoffman–Weeks analysis. The crystallization kinetics of PTMEG were characterized using an Avrami analysis. Mechanistic n values ranged from 2.2 to 2.9 for the primary crystallization process for three molecular weight grades, indicating heterogeneous nucleation of spherulites. Polarized light microscopy confirmed that PTMEG crystallized by the growth of spherulites from heterogeneous nuclei. The half–life for crystallization (t_1/2) and the composite rate constant were found to be dependent on the degree of supercooling (ΔT) and the molecular weight. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of chain architecture on the phase transition of star and cyclic poly(N‐isopropylacrylamide) in water

The heat‐induced phase transition of aqueous solutions of Poly(N‐isopropylacrylamide) (PNIPAM) in water is examined for a four‐arm PNIPAM star (s‐PNIPAM), a cyclic PNIPAM (c‐PNIPAM), and their linear counterparts (l‐PNIPAM) in the case of polymers (1.0 g L^?1) of 12,700 g mol^?1 < M_n < 14,700 g mol^?1. Investigations by turbidity, high‐sensitivity differential scanning calorimetry (HS‐DSC), and light scattering (LS) indicate that the polymer architecture has a strong effect on the cloud point (T_c: decrease for s‐PNIPAM; increase for c‐PNIPAM), the phase transition enthalpy change (ΔH decrease for s‐PNIPAM and c‐PNIPAM), and the hydrodynamic radius of the aggregates formed above T_c (R_H: c‐PNIPAM < s‐PNIPAM < l‐PNIPAM). The properties of s‐PNIPAM are compared with those of previously reported PNIPAM star polymers (3 to 52 arms). The overall observations are described in terms of the arm molecular weight and the local chain density in the vicinity of the core of the star, by analogy with the model developed for PNIPAM brushes on nanoparticles or planar surfaces. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2059–2068.     

Synthesis of AB2 star-shaped miktoarm copolymers and their crystallization behavior

A small molecule (GMS-SA₂) with one alkyl chain and two terminal carboxyl groups was synthesized successfully by the reaction of glyceryl monostearate (GMS) with excess succinic anhydride (SA). Then, GMS-SA₂ was used as a coupling agent to condensate with polyethylene glycols (PEG) of different molecular weight or polyethylene glycol monomethyl ether (PEGm) in the presence of stannous octoate as catalyst and diphenyl ether as azeotropic agent. The AB₂ star-shaped miktoarm copolymers were obtained successfully and were characterized by ¹H-NMR, DSC, GPC, XRD, FTIR and polarizing microscopy. The results of DSC and XRD measurements indicate that the crystallization temperature and the melting temperature of the AB₂ star-shaped miktoarm copolymers are different from those of the corresponding linear PEGs, because the existing of GMS-SA₂ alters their crystalline growth velocity and the perfect degree of crystals. It is very important to control the crystal morphology of star-shaped copolymers by introducing the miktoarm into the starshaped polymers and adjusting its content in star-shaped polymers. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(7): 1365–1370 [译自: 高等学校化学学报]     

Segmented polyethylene oxides: A new class of polyethers prepared via melt transetherification

Several segmented polyethylene oxides (SPEOs) were prepared by a melt-transetherification process using 1,4-bis(methoxymethyl)-2,3,5,6-tetramethylbenzene and polyethylene glycols (PEGs) of different molecular weights (di-, tri-, and tetraethylene glycols and PEGs of molecular weights 300, 600, 1000, 1500, and 3400) as the monomers. The effect of polymerization temperature (185 and 150 °C) on the molecular weight of SPEOs was studied, and it was shown that the molecular weight is larger at a higher polymerization temperature. The reversal of the polycondensation (transetherification) equilibrium by treatment of the polyethers with excess methanol transformed them completely into the starting monomers. The analysis of the degraded products by mass and NMR spectroscopies revealed that side reactions, such as the self-condensation of diols, are insignificant. The polymers containing shorter PEG spacers are amorphous, whereas the ones with longer PEG spacers are semicrystalline. The glass-transition temperature (T_g) of the SPEOs decreased with increases in the spacer length and attained the value of PEO at PEG-600, whereas the melting transition (T_m), crystallization temperature (T_c), and their enthalpies of transition, (ΔH_m) and (ΔH_c), increased with increases in the spacer length. The introduction of “molecular kinks” into SPEOs by the use of another monomer, 1,3-bis(methoxymethyl)-2,4,5,6-tetramethylbenzene, surprisingly, showed little effect on their thermal properties. A “branched-PEO” analogue, containing pendant oligoethyleneoxy units, was also prepared, and its thermal properties were compared with its linear analogue. Preliminary ionic conductance measurements showed that some of these SPEOs could serve as potential candidates for solid polymer–electrolyte applications. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1615–1628, 2001     

Synthesis and characterization of three-arm star-shaped polyethylene glycols with 1,1,1-trihydroxmethylpropane as cores

A small molecule core (TMP-SK₃) with three terminal carboxyl groups was synthesized successfully by the reaction of 1,1,1-trihydroxymethylpropane with the excessive sebacic acid diacetic anhydride (SK). Then, the core molecule was used as a coupling agent to condensate with polyethylene glycols (PEG) of different molecular weights or polyethylene glycol monomethyl ether (PEGm) in the presence of stannous octoate as catalyst and diphenyl ether as an azeotropic agent to remove water. Thus, the three-arm star-shaped PEGs was obtained successfully and characterized by ¹H-NMR, DSC, GPC and XRD etc.. DSC measurements indicate that the crystallizing and the melting temperatures of the three-arm star-shaped PEGs were different from those of the corresponding linear PEG because the existence of TMP-SK₃ altered its crystallizing velocity and perfect degree of crystallization. __________ Translated from Acta Polymerica Sinica, 2007, 9: 862–867 [译自: 高分子学报]     

Long periods in slow-cooled linear and branched polyethylene: Part II

It is shown that the long periods L in slow-cooled polyethylene materials obey the general law L = L⁰ + αr_w, where r_w is the weight average dimension of the coil before crystallization, and L⁰ is a parameter of the order of l_c, the crystalline core thickness, which increases as the cooling rate V decreases. α is a parameter independent of M and V but decreasing with the number of long-chain branches per molecule. The two terms in the above relation are, respectively, the contributions of crystalline and amorphous layers. For cooling rates from 800°C/min to 0.2°C/min, it is shown that the temperature T_c of crystallization is constant; hence the change of morphology (long period, crystalline core thickness, crystallinity) cannot be explained by supercooling. The increase in long period and crystallite thickness in slow-cooled materials with decreasing cooling rate is interpreted in terms of annealing of the crystallized materials between the crystallization temperature T_c and the secondary transition temperature T_αc. Crystallization proceeds by a two-step process of solidification and annealing. During the annealing stage, the mobility of the chains in the crystalline phase is due to defects; the kinetics of thickening is then governed by the mobility (or nucleation) of the defects appearing above T_αc. In the proposed model of crystallization, the assumption that the energy of activation is proportional to T_αc explains the observed laws L ≡ l_c ≡ log t_a, where the annealing time t_a is equal to (T_c ? T_αc)/V. The model applies also to polymers crystallized from the melt and subsequently annealed.     

Ultrahigh Molecular mass Polyethylene/ Carbon Nanotube CompositesCrystallization and melting properties

Ultrahigh molecular mass polyethylene (UHMMPE) is filled with carbon nano-tubes (CNTs) by solution in the presence of maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene copolymer (MA-SEBS) as a compatibilizer. The UHMMPE/CNT composites crystallized from melt were prepared at a cooling rate of 20°C min^-1. The melting and crystallization behaviors of UHMMPE/ CNT composites were investigated by differential scanning calorimetry. The results showed that onset melting temperature (T _m) and degree of crystallinity (X _c) of UHMMPE/CNT composites crystallized from solution are higher than those from melt due to the larger crystalline lamellar thickness. The onset crystallization temperature (T _c) of UHMMPE/CNT composites tends to shift to higher temperature region with increasing CNT content in the composites. Tm and Tc of UHMMPE phase in UHMMPE/CNT composites decrease with the addition of MA-SEBS. Moreover, the crystallization rate of UHMMPE phase in UHMMPE/CNT composite is increased due to the introduction of CNTs. MA-SEBS acts as compatilizer, enhances the dispersion of CNTs in the UHMMPE matrix. Thereby, the crystallization rate of UHMMPE phase in UHMMPE/CNT composite is further increased with the addition of MA-SEBS. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of non-isothermal crystallization of amorphous Cu<Subscript>50</Subscript>Ti<Subscript>50</Subscript> alloy

The crystallization kinetics of amorphous Cu₅₀Ti₅₀ has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions. The curves at different linear heating rates (2, 4, 8 and 16 K min^–1) show sharp crystallization peaks. The crystallization peak shifts to higher temperatures with increasing heating rate. The Kissingers method of analysis of the shift in the transformation peak is applied to evaluate the activation energy (E _c). The KJMA formalism, which is basically developed for isothermal experiments, is also used to obtain E _c and the Avrami parameter (n).The DSC data have been analysed in terms of kinetic parameters, viz. activation energy (E _c), Avrami exponent (n) and frequency factor K ₀ using three different theoretical models. It is observed that the activation energy values derived from KJMA approach and modified Kissinger equation agree fairly well with each other. The activation energy values obtained from normal Kissinger method, and Gao and Wang expression underestimate the activation energy.The financial support provided by All India Council for Technical Education (AICTE), New Delhi (Govt. of India) is gratefully acknowledged.     

Oxidative NHC-Catalysis as Organocatalytic Platform for the Synthesis of Polyester Oligomers by Step-Growth Polymerization

The application of N-heterocyclic carbene (NHC) catalysis to the polycondensation of diols and dialdehydes under oxidative conditions is herein presented for the synthesis of polyesters using fossil-based (ethylene glycol, phthalaldehydes) and bio-based (furan derivatives, glycerol, isosorbide) monomers. The catalytic dimethyl triazolium/1,8-diazabicyclo[5.4.0]undec-7-ene couple and stoichiometric quinone oxidant afforded polyester oligomers with a number-average molecular weight (M_n) in the range of 1.5–7.8 kg mol⁻¹ as determined by NMR analysis. The synthesis of a higher molecular weight polyester (polyethylene terephthalate, PET) by an NHC-promoted two-step procedure via oligoester intermediates is also illustrated together with the catalyst-controlled preparation of cross-linked or linear polyesters derived from the trifunctional glycerol. The thermal properties (TGA and DSC analyses) of the synthesized oligoesters are also reported.     

Intrinsic viscosity of polymers of low molecular weight

Experimental evidence concerning the dependence of the intrinsic viscosity [η] on molecular weight M in the low molecular weight range (from oligomers to M = 5 × 10⁴) has been collected in a variety of solvents for about ten polymers, i.e., polyethylene, poly(ethylene oxide), poly(propylene oxide), polydimethylsiloxane, polyisobutylene, poly(vinylacetate), poly(methyl methacrylate), polystyrene, poly-α-methylstyrene, and some cellulose derivatives. In theta solvents, the constancy of the ratio [η]Θ/M^0.5 extends down to values of M much lower than those predicted by current hydrodynamic theories. In good solvents, and on decreasing M, the polymers examined, with the exception of polyethylene and some cellulose derivatives, show a decrease in the exponent a of the Mark-Houwink equation [η] = KM^a. This upward curvature gives rise to the existence of a more or less extended linear region where the equation [η] = K₀M^0.5 is obeyed. Below the linear range, i.e., for even shorter chains, the exponent a can increase, i.e., polydimethylsiloxane, or decrease below 0.5, i.e., poly(ethylene oxide), depending on the particular chain properties. These different dependences have been discussed in terms of: (a) variations of thermodynamic interactions with molecular weight; (b) variations of conformational characteristics (as for instance the ratio) 〈r0²/nl²〉, where 〈r0²〉 is the unperturbed mean square end-to-end distance and n is the number of bonds each of length l; (c) hydrodynamic properties of short chains.     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271