Original Article

The dilute solution properties of poly(d,l-lactide)s (PDL50) with a weight-averaged molar mass (M_w) ranging from 0.154 × 10⁴ to 75.7 × 10⁴ g mol⁻¹ are thoroughly studied in tetrahydrofuran at 25 °C by static light and small-angle X-ray scattering and intrinsic viscosity ([η]) measurements. The M_w dependences of 〈S²〉_z^1/2 and [η] are quantitatively described by the wormlike cylinder with stiffness parameter λ⁻¹ = 2.9 nm, indicating that the PDL50 chain behaves as a typical flexible polymer but is essentially 1.6−2.1 times stiffer than polystyrene and poly(methyl methacrylate).

Polymeric micelles based on amphiphilic poly(ethylene oxide)-b-poly(ε-caprolactone)-b-poly(ethylene oxide)(PEO-b-PCL-b-PEO) triblock copolymers improved the solubility of caffeic acid phenethyl ester (CAPE) in aqueous media. Further on, the grafting of pendant cinnamyl moieties to the PCL block enhanced the compatibility between CAPE and the micellar core, thus increasing the encapsulation efficiency and reducing the burst release effect as compared to those of micelles with an unmodified PCL core.

The interfacial adhesion between olefinic double bond- or hydroxyl-terminated telechelic polypropylenes (PPs) and carbon fibers was studied to determine the potential of the telechelic PPs as a candidate for PP matrix resin-coupling agents for carbon fiber-reinforced PP composites. The hydroxyl-terminated PP showed higher interfacial shear strength than that of commercial PP and olefinic double bond-terminated PP. The hydroxyl-terminated PP could be used as a novel coupling agent of the PP matrix.

A cyclic block copolymer allows feasible fabrication of porous films through designed interaction between its macromolecular arms. The morphology of pores is directly determined by the structural features of the block copolymer and can be easily tuned by modification of the length of its ring and arms.

The correlation between mechanical properties and structural changes upon uniaxial stretching was studied by atomic force microscopy observations and two-dimensional small-angle X-ray scattering measurements. For this purpose, coated layers composed of di- and tri-block copolymer blends were prepared by solution coating at different drying temperatures. The packing regularity of spherical microdomains in the stretching direction was enhanced with stretching. We could correlate fracture of the block copolymer film having spherical microdomains with the completion of stretching-induced ordering of spheres in the stretching direction, which sensitively depended on the drying temperature.

Photopolymerization of dodecyl acrylate was conducted using methyl phenylglyoxylate as an initiator. Most polymers had either an acryloyl group or a benzoyl group at one of the chain ends. We investigated the initiation pathways and found out that methyl phenylglyoxylate initiated photopolymerization only by Norrish type II processes.

Transient elongational viscosity for polypropylene (PP)/low-density polyethylene (LDPE) blends was evaluated. Because deformed LDPE droplets act as rigid fibers due to its strain hardening, the blends show a strain hardening behavior. The growth curves are, however, affected by their viscosity ratio. These behaviors are calculated by the Phan–Thien Tanner model by assuming a symmetric geometry with a periodic structure. Based on the simulation, we propose an appropriate LDPE to modify the processability, at which the strain hardening in the elongational viscosity is required.

The osmotic pressure during the gelation process below the overlapping concentration of prepolymers was investigated using a series of model polymer gels, namely, tetra-polyethylene glycol gels. The osmotic pressure decreased during the gelation reaction and was constant after the sol–gel transition, suggesting that the clusters grow and fill the system, at the sol–gel transition point. This representation of the sol–gel transition at the overlapping condition of the critical clusters corresponds well to the aggregation process prediction.

Low-modulus polypropylene (LMPP) with controlled stereoregularity showed elastic recovery. To understand the underlying mechanism, changes in the morphology of LMPP under cyclic uniaxial elongation were investigated using in situ SAXS and WAXD. During the first cycle, the undulating structure of the crystal lamellae is large, and fragmentation of the lamellae occurs. On the other hand, during the second cycle, the little fragmentation of the lamellae occurs and that only the lamellae were rotating under elongation. Based on these results, lamella fragmentation has a significant effect on the elastic-recovery rate.

Visible light-curable alginate was prepared by coupling alginate with furfurylamine. The prepared furfuryl alginate (F-Alginate) underwent gelation in the presence of a photosensitizer under visible light irradiation. The mechanical and release properties of the visible light-induced gel were similar to that of conventional Ca²⁺-induced cross-linked alginate. The release rate of encapsulated substances depended on their molecular weight. Cell growth was enhanced in response to a sustained release of insulin-like growth factor-1 from the F-Alginate hydrogel.

To understand the roles of mechanical and structural factors in the extracellular matrix on cancer cell migration, elasticity/porosity-tunable gel matrices of gelatinous microfibers were developed. The elasticity of fibers and the porosity of matrix were tuned with photocrosslinking conditions and degree of interfiber bonding, respectively. Highly malignant MDA-MB-231 cells showed the highest degree of MMP-independent invasion into the matrix composed of fibers with a Young’s modulus of 20 kPa and a low degree of interfiber bonding, while nontumorigenic MCF-10A cells did not show invasive behavior under the same matrix conditions.

Hydrophilic alternating copolymers (P(11EO/MA)_m) of methoxy poly(ethylene glycol) allyl ether (11EO) and maleic anhydride (MA) were prepared via controlled radical polymerization. The MA units in P(11EO/MA)_m were hydrolyzed to prepare pendant carboxylic acid group-containing polymers (P(11EO/MH)_m). Furthermore, an amphiphilic diblock copolymer (P(11EO/MH)_m-PS_n) was prepared via block copolymerization of styrene using P(11EO/MH)_m as a macro-chain transfer agent. The association behavior of P(11EO/MH)_m-PS_n in water was also investigated.

A π-conjugated polymer based on thienylene–vinylene–thienylene (TVT) units can form a thermotropic liquid-crystalline (LC) mesophase over a wide temperature range. Thermal annealing at LC temperatures strongly enhanced hole mobilities in organic field-effect transistors (OFETs) owing to improved molecular ordering. Because of its thermoplasticity, the TVT-based π-conjugated polymer can also be processed into semiconducting fine microfibers and serve as a charge transport pathway in microfiber OFETs.

Active, hydrophilic, piezoelectric PLLA surface is formed by correlating processing parameters with etching and annealing as post-processing steps. Optimal design is obtained after uniaxial drawing of films for five times their length at 90 °C with 40 mm min⁻¹ drawing rate and post-processing heat treatment at 140 °C followed by surface alkaline etching. We designed active PLLA film with high potential for intensive interactions with cells, very important for further biomedical applications, including exploring the effect of piezoelectricity on cell proliferation.

Herein, several synthetic procedures for the synthesis of uniform PEGs were compared. The importance of SEC as analytical method for the determination of the precise structure and purity of uniform PEGs was shown by means of simple symmetry peak analysis, revealing that SEC can detect contaminations of only 2% of oligomers with only one repeat unit difference.

Schwiertz et al. report on the synthesis of miktoarm star polymers based on polypept(o)ides by nucleophilic ring opening polymerization of N-carboxyanhydrides. The reported procedures allow for precise control over chain length, number of arms and end group functionality.

The epoxydized soybean oil grafted with CTBN (ESO-g-CTBN) was synthesized from ring opening reaction between epoxide group and carboxyl group. The ESO-g-CTBN help to improve the fracture toughness of epoxy resin by the mechanism as shown in the figure.

By virtue of “core first” method, ABC star quaterpolymers were controllably synthesized by combination of controlled polymerization and thiolactone chemistry. The miktoarm stars were responsive to temperature, pH, CO₂, O₂ and oxidation, and thus the phase transition temperature, size and morphology of copolymer assemblies could be efficiently tuned via adopting a single stimulus or combined stimuli.

The sulfur-containing styrene derivative, 4-methylenethiochromane (META), was subjected to anionic copolymerization with isoprene (Ip) modified with different additives. The reactivity of META can be effectively regulated with additives; thus, the regulation of the alternating or gradient copolymerization of META and Ip was facilely realized through the use of additives.

An efficient and straightforward strategy for the synthesis of uniform, sequence-defined oligo(ester-amide-ester)s via sequential nucleophilic substitution reactions and Passerini reaction was developed. The side groups could be easily regulated by the Passerini reaction of different aldehydes. The synthesis of uniform, symmetrical, long-chain oligomers was further demonstrated by an iterative approach. The DIC/DPTS-mediated polycondensation of the α,ω-hydroxy carboxylic acids as the sequence-defined oligomer afforded high-molecular-weight periodic poly(ester-amide-ester)s. The thermal properties of these oligo/poly(ester-amide-ester)s were also examined.