Conversion of Face‐On Orientation to Edge‐On/Flat‐On in Induced‐Crystallization of Poly(3‐hexylthiophene) via Functionalization/Grafting of Reduced Graphene Oxide with Thiophene Adducts

Reduced graphene oxide (rGO) is functionalized with 2‐thiophene acetic acid (rGO‐f‐TAA) and grafted with poly(3‐dodecylthiophene) (rGO‐g‐PDDT) and poly(3‐thiophene ethanol) (rGO‐g‐PTEt) to manipulate the orientation and patterning of crystallized poly(3‐hexylthiophene) (P3HT). P3HT chains prefer to interact with their thiophene rings with bared rGO surface, resulting in a conventional face‐on orientation. In these hybrids, beyond critical length of P3HT nanofibers developed onto rGO (>100 nm), an inclination occurs after solvent evaporation, thereby face‐on noninclined fibers change to edge‐on inclined ones. In P3HT/rGO‐f‐TAA supramolecular structures patterned with P3HT short nanofibrils (42–95 nm in length), the orientation of P3HT chains changes from face‐on to edge‐on, originating from strong interactions between hexyl side chains of P3HTs and 2‐thiophene acetic acid functional groups of rGO. Supramolecular structures based on grafted rGO demonstrate a patched‐like morphology composed of flat‐on P3HTs with main backbones perpendicular to substrate. Grafted polythiophenic oligomers onto rGO (rGO‐g‐PDDT and rGO‐g‐PTEt) provoke P3HT backbones to vertically attach to surface and remain perpendicular even after solvent evaporation. Flat‐on orientation acquired for rGO‐g‐PDDT and rGO‐g‐PTEt systems is the best for P3HT chains assembled onto rGO. Face‐on P3HT/rGO hybrids and, subsequently, edge‐on P3HT/rGO‐f‐TAA hybrids also reflect optical and supramolecular donor–acceptor properties based on ultraviolet–visible and photoluminescence analyses.     

Amphiphilic Block Copolymers Containing Regioregular Poly(3‐hexylthiophene) and Poly(2‐ethyl‐2‐oxazoline)

Poly(3‐hexylthiophene)‐block‐poly(2‐ethyl‐2‐oxazoline) amphiphilic rod–coil diblock copolymers have been synthesized by a combination of Grignard metathesis (GRIM) and ring‐opening cationic polymerization. Diblock copolymers containing 5, 15, and 30 mol‐% poly(2‐ethyl‐2‐oxazoline) have been synthesized and characterized. The synthesized rod–coil block copolymers display nanofibrillar morphology where the density of the nanofibrills is dependent on the concentration of the poly(2‐ethyl‐2‐oxazoline) coil segment. The conductivity of the diblock copolymers was lowered from 200 to 35 S · cm^?1 with an increase in the content of the insulating poly(2‐ethyl‐2‐oxazoline) block. By contrast, the field‐effect mobility decreased by 2–3 orders of magnitude upon the incorporation of the poly(2‐ethyl‐2‐oxazoline) insulating segment.

     

Poly(ε‐caprolactone) Single Crystals with Different Aspect Ratios Mediated by Counterion Exchange on the Basis of Hofmeister Series

Although polymeric single crystals fabricated from self‐assembly of block copolymers are reported, preparation of single crystals with different aspect ratios still remains a major challenge. In this work, a facile way is demonstrated to prepare poly(ε‐caprolactone) based single crystals with tunable aspect ratios through simple counterion exchange on the basis of the Hofmeister series. Briefly, after ion exchange from Brˉ (an ion‐containing triblock copolymer, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(quaternized 2‐(dimethylamino)ethyl methacrylate)/ethyl bromide (PEO‐b‐PCL‐b‐qPDM‐Br)) to more hydrophobic anions, Iˉ, SCNˉ, PF₆ˉ and OTfˉ, respectively, morphological transitions from spheres to wormlike micelles and sphere to 2D platelet structure with an increasing aspect ratio are observed. The morphological transition depends on the essential hydrophilicity of the qPDM‐X segment and increasing crystallinity of the PCL core caused by ion exchange. These findings provide a facile approach to the preparation of polymeric single crystals with tunable aspect ratios.     

Synthesis and Characterization of Comb‐Like Copolymers Based on Poly(ε‐caprolactone) and Poly(α‐olefin)

Comb‐like copolymers based on a polyolefin backbone of poly(10‐undecene‐1‐ol) (PUol) with poly(ε‐caprolactone) (PCL) side chains are synthesized in two steps. After synthesis of PUol by metallocene‐catalyzed polymerization, the side‐chain hydroxyl functionalities of this polar polyolefin are used as an initiator for the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). In this context, copolymers with different lengths of PCL grafts are prepared. The chemical structure and the composition of the synthesized copolymers are characterized by ¹H and ¹³C NMR spectroscopy. It is shown that the hydroxyl end groups of PUol act effectively as initiating sites for the CL ROP. Size‐exclusion chromatography (SEC) measurements confirm the absence of non‐attached PCL and the expected increase in molar mass after grafting. The thermal and decomposition behaviors are investigated by DSC and thermogravimetric analysis (TGA). The effect of the length of the PCL grafts on the crystallization behavior of the comb‐like copolymers is investigated by DSC and wide‐angle X‐ray scattering (WAXS).

     

Preparation of Block Copolymers with a Single Tg Based on Segments of Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) and Polycarbonate of Bisphenol A

Summary: The synthesis and the properties of block copolymers based on PPO and PC segments are reported. Copolymers that have a multi‐block structure are synthesized by a polycondensation reaction that employs oligomeric PPO and PC diol terminated with phosgene or bischloroformate of bisphenol A. In the reaction scheme two steps are involved: first, the reaction of one of the oligomeric diols (PPO or PC) with the bischloroformate or phosgene; second, the oligomeric bischloroformate is reacted with the other diol. The molecular characteristics of the prepared samples are studied by SEC, ¹H and ¹³C NMR, and FT‐IR spectroscopy. The thermal and rheological properties and the thermal stability have also been investigated by means of DSC, rotational rheometry, and TGA, respectively. Polymers that have a single glass transition temperature are obtained if low‐molecular‐weight segments are used. From a rheological point of view, these materials show a remarkably lower melt viscosity compared with a PPO homopolymer that has a comparable average molecular weight.

Rheometric curves of PPO‐b‐PC (3) compared with a commercial PPO.     

Fractionation and Characterisation of Propylene‐Ethylene Random Copolymers: Effect of the Comonomer on Crystallisation of Poly(propylene) in the γ‐Phase

Summary: Three propylene‐ethylene random copolymers, of varying ethylene content, were fractionated using preparative TREF. The TREF fractions were subsequently analysed offline by CRYSTAF, DSC, ¹³C NMR spectroscopy, HT‐GPC, and WAXD. The effect of the ethylene comonomer on the crystallisability of the propylene was investigated, along with the effect of the comonomer on the type of crystal phase formed during the crystallisation. The results show that the comonomer inhibits the crystallisation of the copolymer and that as the ethylene content increases, the crystallisation and melting points decrease. It was also shown that the higher the ethylene content, the more of the γ‐phase crystal type is formed. The inter‐molecular distribution of the ethylene comonomer and stereo errors vary between the samples analysed, and this accounts for the relative differences in crystallisation behaviour of the samples.

¹³C NMR of propylene‐ethylene random copolymer.     

Synthesis of Grafted Block Copolymers Based on ε‐Caprolactone: Influence of Branches on Their Thermal Behavior

Branched copolymers are a special class of polymeric materials in which are reflected the combined effects of polymer segments and architectural constraints of the branched architecture. This study employed two methodologies to obtain copolymers with different branching density. In the first case, poly(hydroxyethyl methacrylate‐graft‐poly(ε‐caprolactone)‐block‐poly(ε‐caprolactone), P(HEMA‐g‐PCL)‐b‐PCL, copolymers were synthesized by a “grafting through” method in a three‐step reaction pathway involving ring opening polymerization (ROP) and radical addition fragmentation transfer (RAFT) polymerization. In the second case, a combination of simultaneous “grafting through” and “grafting from” methods in a one‐pot RAFT and ROP reaction afforded P(HEMA‐co‐HEMA‐g‐PCL)‐b‐PCL comb‐like copolymers with comparatively less dense branching. Samples with molar masses between 5500 and 46 000 g mol^?1 and polydispersity indexes (M_w/M_n) lower than 1.3 were successfully obtained through both approaches. According to thermal analyses, the presence of branches reduces PCL melting temperature by as much as 20 °C, without affecting thermal stability. This fact was particularly evident for the most densely branched copolymers with higher molar masses. Nonisothermal crystallization process was successfully described using Ozawa's method, which showed a clear dependence of crystallization rate and cooling on grafting density.

     

Preparation and Properties of Degradable Shape Memory Material Based on Partial α‐Cyclodextrin–Poly(ε‐caprolactone) Inclusion Complex

A series of supramolecular degradable inclusion complex (IC) films were formed by threading α‐cyclodextrin (α‐CD) molecules over poly(ε‐caprolactone) (PCL) according to the designed ratio of α‐CD–PCL. Due to containing both α‐CD–PCL inclusion crystallites and uncovered PCL crystallites, the resulting supramolecular α‐CD–PCL IC partial films displayed a shape memory effect. The properties of the materials were investigated by ¹H NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling measurement. It was found that the casting temperature and solvent have great influence on the formation and properties of the α‐CD–PCL partial ICs. The modes of complexes on different conditions were proposed. In addition, the introduction of inclusion structure accelerates the degradation of materials strongly.