Polymer Nanostructures Research Articles

Using design of experiments (DoE) to optimize performance and stability of biomimetic cell membrane-coated nanostructures for cancer therapy.

Introduction: Cell membrane-covered biomimetic nanosystems have allowed the development of homologous nanostructures to bestow nanoparticles with enhanced biointerfacing capabilities. The stability of these structures, however, still represents a challenge for the scientific community. This study is aimed at developing and optimizing cell derived membrane-coated nanostructures upon applying design of experiments (DoE) to improve the therapeutic index by homotypic targeting in cancer cells. Methods: Important physicochemical features of the extracted cell membrane from tumoral cells were assessed by mass spectrometry-based proteomics. PLGA-based nanoparticles encapsulating temozolomide (TMZ NPs) were successfully developed. The coating technology applying the isolated U251 cell membrane (MB) was optimized using a fractional two-level three-factor factorial design. All the formulation runs were systematically characterized regarding their diameter, polydispersity index (PDI), and zeta potential (ZP). Experimental conditions generated by DoE were also subjected to morphological studies using negative-staining transmission electron microscopy (TEM). Its short-time stability was also assessed. MicroRaman and Fourier-Transform Infrared (FTIR) spectroscopies and Confocal microscopy were used as characterization techniques for evaluating the NP-MB nanostructures. Internalization studies were carried out to evaluate the homotypic targeting ability. Results and Discussion: The results have shown that nearly 80% of plasma membrane proteins were retained in the cell membrane vesicles after the isolation process, including key proteins to the homotypic binding. DoE analysis considering acquired TEM images reveals that condition run five should be the best-optimized procedure to produce the biomimetic cell-derived membrane-coated nanostructure (NP-MB). Storage stability for at least two weeks of the biomimetic system is expected once the original characteristics of diameter, PDI, and ZP, were maintained. Raman, FTIR, and confocal characterization results have shown the successful encapsulation of TMZ drug and provided evidence of the effective coating applying the MB. Cell internalization studies corroborate the proteomic data indicating that the optimized NP-MB achieved specific targeting of homotypic tumor cells. The structure should retain the complex biological functions of U251 natural cell membranes while exhibiting physicochemical properties suitable for effective homotypic recognition. Conclusion: Together, these findings provide coverage and a deeper understanding regarding the dynamics around extracted cell membrane and polymeric nanostructures interactions and an in-depth insight into the cell membrane coating technology and the development of optimized biomimetic and bioinspired nanostructured systems.

Polymeric Nanoparticles as a Self‐Adjuvanting Peptide Vaccine Delivery System: The Role of Shape

AbstractAntigens incorporated in subunit vaccines are typically poorly immunogenic, so a strong immunostimulant (adjuvant) and/or delivery system is required to boost immunogenicity. In this work, the various functional polymer nanostructures, that is, rods, worms, spheres, and tadpoles are used to develop potent peptide antigen delivery systems. The antigen PADRE‐J8 (PJ8), derived from Group A Streptococcus (GAS) M‐protein, is either physically mixed or chemically conjugated to polymeric nanoparticles of different shapes. The physical mixture of polymeric nanoparticles and antigen is more effective in inducing antibody production than their chemical conjugates. Moreover, rod‐shaped polymeric nanoparticles in physical mixture with PJ8 elicited higher and more opsonic antibody titers than powerful complete Freund's adjuvant (CFA)‐adjuvanted antigen. Herein, for the first time it is demonstrated that a) the block copolymer, in nanoparticle form, can act as an immune adjuvant, b) nanoparticle shape plays a crucial role in their immunogenicity, and c) antigen conjugation is not required, nor is antigen encapsulation or absorption.

Efficient full solar spectrum-driven photocatalytic hydrogen production on low bandgap TiO2/conjugated polymer nanostructures.

The development of photocatalysts that can utilize the entire solar spectrum is crucial to achieving efficient solar energy conversion. The utility of the benchmark photocatalyst, TiO2, is limited only to the UV region due to its large bandgap. Extending the light harvesting properties across the entire spectrum is paramount to enhancing solar photocatalytic performance. In this work, we developed low bandgap TiO2/conjugated polymer nanostructures which exhibit full spectrum activity for efficient H2 production. The highly mesoporous structure of the nanostructures together with the photosensitizing properties of the conjugated polymer enabled efficient solar light activity. The mesoporous TiO2 nanostructures calcined at 550 °C exhibited a defect-free anatase crystalline phase with traces of brookite and high surface area, resulting in the best performance in hydrogen production (5.34 mmol g-1 h-1) under sunlight simulation. This value is higher not only in comparison to other TiO2-based catalysts but also to other semiconductor materials reported in the literature. Thus, this work provides an effective strategy for the construction of full spectrum active nanostructured catalysts for enhanced solar photocatalytic hydrogen production.

Tuning the nanostructure and molecular orientation of high molecular weight diketopyrrolopyrrole-based polymers for high-performance field-effect transistors.

As a versatile class of semiconductors, diketopyrrolopyrrole (DPP)-based conjugated polymers are well suited for applications of next-generation plastic electronics because of their excellent and tunable optoelectronic properties via a rational design of chemical structures. However, it remains a challenge to unravel and eventually influence the correlation between their solution-state aggregation and solid-state microstructure. In this contribution, the solution-state aggregation of high molecular weight PDPP3T is effectively enhanced by solvent selectivity, and a fibril-like nanostructure with short-range and long-range order is generated and tuned in thin films. The predominant role of solvent quality on polymer packing orientation is revealed, with an orientational transition from a face-on to an edge-on texture for the same PDPP3T. The resultant edge-on arranged films lead to a significant improvement in charge transport in transistors, and the field-effect hole mobility reaches 2.12 cm2 V-1 s-1 with a drain current on/off ratio of up to 108. Our findings offer a new strategy for enhancing the device performance of polymer electronic devices.

Imprinted Polymer Functionalized Concatenated Optical Microfiber: Hypersensitive and Selective

Optical interferometry integrated with molecularly imprinting polymer (MIP) can be an advanced futuristic approach for developing ultrasensitive and selective remote detection technology. This cohesive strategy has enormous potential for developing next-generation online biomolecule detection systems riding on the benefits of artificial complementary polymeric nanostructure with outstanding durability, easy synthesis process, and sustainability in harsh environmental conditions. Here, we have reported a label-free, hypersensitive, online, and selective biodetection method by combining a concatenated microfiber interferometer and an artificial molecular receptor-based imprinting technique to develop an imprinted polymer functionalized optical sensor for precise determination of water pollutant 4-nitrophenol (4-NP) in aqueous media with a dynamic detection range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{12}}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{4}}$ </tex-math></inline-formula> M. The proposed imprinted polymer functionalized optical sensor exhibits a hypersensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.14\times 10^{{11}}$ </tex-math></inline-formula> nm/M and a minimum detection limit of 1.628 fM. The compact size, fast response, repeatable behavior, and highly selective label-free detection nature of the developed system will pave a new path for selective biosensing, water quality monitoring, and environmental research applications.

Topology-controlled self-assembly of amphiphilic block copolymers.

Contemporary synthetic chemistry approaches can be used to yield a range of distinct polymer topologies with precise control. The topology of a polymer strongly influences its self-assembly into complex nanostructures however a clear mechanistic understanding of the relationship between polymer topology and self-assembly has not yet been developed. In this work, we use atomistic molecular dynamics simulations to provide a nanoscale picture of the self-assembly of three poly(ethylene oxide)-poly(methyl acrylate) block copolymers with different topologies into micelles. We find that the topology affects the ability of the micelle to form a compact hydrophobic core, which directly affects its stability. Also, we apply unsupervised machine learning techniques to show that the topology of a polymer affects its ability to take a conformation in response to the local environment within the micelles. This work provides foundations for the rational design of polymer nanostructures based on their underlying topology.

Nanostructures as Photothermal Agents in Tumor Treatment.

Traditional methods of tumor treatment such as surgical resection, chemotherapy, and radiation therapy have certain limitations, and their treatment effects are not always satisfactory. As a new tumor treatment method, photothermal therapy based on nanostructures has attracted the attention of researchers due to its characteristics of minimally invasive, low side effects, and inhibition of cancer metastasis. In recent years, there has been a variety of inorganic or organic nanostructures used in the field of photothermal tumor treatment, and they have shown great application prospects. In this paper, the advantages and disadvantages of a variety of nanomaterials/nanostructures as photothermal agents (PTAs) for photothermal therapy as well as their research progress are reviewed. For the sake of clarity, the recently reported nanomaterials/nanostructures for photothermal therapy of tumor are classified into five main categories, i.e., carbon nanostructures, noble metal nanostructures, transition metal sulfides, organic polymer, and other nanostructures. In addition, future perspectives or challenges in the related field are discussed.

Electrodeposition of One-Dimensional Nanostructures: Environmentally Friendly Method

During the past decade, nanotechnology has become an active field of research because of its huge potential for a variety of applications. When the size of many established, well-studied materials is reduced to the nanoscale, radically improved or new surprising properties often emerge. There are mainly four types of nanostructures: zero, one, two and three dimensional structures. Among them, one-dimensional (1D) nanostructures have been the focus of quite extensive studies worldwide, partially because of their unique physical and chemical properties. Compared to the other three dimensional structures, the first characteristic of 1D nanostructure is its smaller dimension structure and high aspect ratio, which could efficiently transport electrical carriers along one controllable direction; as a consequence they are highly suitable for moving charges in integrated nanoscale systems. The second characteristic of 1D nanostructure is its device function, which can be exploited as device elements in many kinds of nanodevices. Indeed it is important to note that superior physical properties including superconductivity, enhanced magnetic coercivity and the unusual magnetic state of some 1D nanostructures have been theoretically predicted and some of them have already been confirmed by experiments. In order to attain the potential offered by 1D nanostructures, one of the most important issues is how to synthesize 1D nanostructures in large quantities with a convenient method. Many synthetic strategies, such as solution or vapor-phase approaches, template-directed methods, electrospinning techniques, solvothermal syntheses, self-assembly methods, etc., have been developed to fabricate different classes of 1D nanostructured materials, including metals, semiconductors, functional oxides, structural ceramics, polymers and composites. All the methods can be divided into two categories: those carried out in a gas phase (i.e., “dry processes”) and those carried out in a liquid phase (i.e., “wet processes”). The dry processes include, for example, techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), pulse laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). In general, these gas phase processes require expensive and specialized equipments. The wet processes include sol-gel method, hydrothermal method, chemical bath deposition (CBD) and electrodeposition. Among the above mentioned methods, electrodeposition has many advantages such as low cost, environmentally friendly, high growth rate at relatively low temperatures and easier control of shape and size. Generally, there are two strategies to produce the 1D nanostructures through the electrochemical process. They are the template-assisted electrodeposition, and the template-free electrodeposition. In this chapter, we will approach the recent progress and offer some prospects of future directions in electrodeposition of 1D nanostructures. Electrodeposition is a simple and flexible method for the synthesis of one-dimensional (1D) nanostructures and has attracted great attention in recent years.

Tuning Plasmonic Properties of Gold Nanoparticles by Employing Nanoscale DNA Hydrogel Scaffolds

Noble metals have always fascinated researchers due to their feasible and facile approach to plasmonics. Especially the extensive utilization of gold (Au) has been found in biomedical engineering, microelectronics, and catalysis. Surface plasmonic resonance (SPR) sensors are achievable by employing plasmonic nanoparticles. The past decades have seen colossal advancement in noble metal nanoparticle research. Surface plasmonic biosensors are advanced in terms of sensing accuracy and detection limit. Likewise, gold nanoparticles (AuNPs) have been widely used to develop distinct biosensors for molecular diagnosis. DNA nanotechnology facilitates advanced nanostructure having unique properties that contribute vastly to clinical therapeutics. The critical element for absolute control of materials at the nanoscale is the engineering of optical and plasmonic characteristics of the polymeric and metallic nanostructure. Correspondingly, AuNP's vivid intense color expressions are dependent on their size, shape, and compositions, which implies their strong influence on tuning the plasmonic properties. These plasmonic properties of AuNPs have vastly exerted the biosensing and molecular diagnosis applications without any hazardous effects. Here, we have designed nanoscale X-DNA-based Dgel scaffolds utilized for tuning the plasmonic properties of AuNPs. The DNA nanohydrogel (Dgel) scaffolds engineered with three different X-DNAs of distinct numbers of base pairs were applied. We have designed X-DNA base pair-controlled size-varied Dgel scaffolds and molar ratio-based nano assemblies to tune the plasmonic properties of AuNPs. The nanoscale DNA hydrogel's negatively charged scaffold facilitates quaternary ammonium ligand-modified positively charged AuNPs to flocculate around due to electrostatic charge attractions. Overall, our study demonstrates that by altering the DNA hydrogel scaffolds and the physical properties of the nanoscale hydrogel matrix, the SPR properties can be modulated. This approach could potentially benefit in monitoring diverse therapeutic biomolecules.

Quantitative phase contrast imaging with a nonlocal angle-selective metasurface

Phase contrast microscopy has played a central role in the development of modern biology, geology, and nanotechnology. It can visualize the structure of translucent objects that remains hidden in regular optical microscopes. The optical layout of a phase contrast microscope is based on a 4 f image processing setup and has essentially remained unchanged since its invention by Zernike in the early 1930s. Here, we propose a conceptually new approach to phase contrast imaging that harnesses the non-local optical response of a guided-mode-resonator metasurface. We highlight its benefits and demonstrate the imaging of various phase objects, including biological cells, polymeric nanostructures, and transparent metasurfaces. Our results showcase that the addition of this non-local metasurface to a conventional microscope enables quantitative phase contrast imaging with a 0.02π phase accuracy. At a high level, this work adds to the growing body of research aimed at the use of metasurfaces for analog optical computing.

Multimodal STEM Investigation of Polymer Damage Processes Induced by Electron Beam Irradiation

Abstract Self-assembled polymer nanostructures are useful for many applications, including biomedicine, energy, and sensing, often presenting a more stable and customizable alternative for drug delivery than lipid-based assemblies, like liposomes. Polyethylene glycol-b-poly(propylene sulfide) (PEG-b-PPS) nanostructures are an example of a cutting-edge self-assembled polymer system. Here, to better understand the impact of electron irradiation on the molecular and macroscale structure, we utilize analytical scanning transmission electron microscopy. Through electron energy-loss spectroscopy (EELS), we access information regarding the degradation of PEG-b-PPS self-assembled polymers under the electron beam. By coupling the spatial and temporal resolution afforded by EELS, we describe the movement of elements in the polymer system during radiolysis and propose a mechanism for sample degradation. We believe this work will serve as a blueprint to determine the effects of electron irradiation on polymer architectures via spectroscopy.

Synthesis of PVA/Fe3O4@SiO2@CPS@SID@Ni as novel magnetic fibrous composite polymer nanostructures and evaluation of anti-cancer and antimicrobial activity

Synthesis of PVA/Fe3O4@SiO2@CPS@SID@Ni as novel magnetic fibrous composite polymer nanostructures and evaluation of anti-cancer and antimicrobial activity

Local Piezoelectric Response of Polymer/Ceramic Nanocomposite Fibers.

Effective converse piezoelectric coefficient (d33,eff) mapping of poly(vinylidene fluoride) (PVDF) nanofibers with ceramic BaTiO3 nanoparticle inclusions obtained by electrospinning was carried out by piezoresponse force microscopy (PFM) in a peculiar dynamic mode, namely constant-excitation frequency-modulation (CE-FM), particularly suitable for the analysis of compliant materials. Mapping of single nanocomposite fibers was carried out to demonstrate the ability of CE-FM-PFM to investigate the nanostructure of semicrystalline polymers well above their glass transition temperature, such as PVDF, by revealing the distribution of piezoelectric activity of the nanofiber, as well as of the embedded nanoparticles employed. A decreased piezoelectric activity at the nanoparticle site compared to the polymeric fiber was found. This evidence can be rationalized in terms of a tradeoff between the dielectric constants and piezoelectric coefficients of the component materials, as well as on the mutual orientation of polar axes.

Intrinsic low-dielectric constant and low-dielectric loss aliphatic-aromatic copolyimides: The effect of chemical structure

Low-dielectric polymer materials are becoming essential for 5 G mobile communication to achieve mass transport information without signal loss. Herein, we present an aliphatic–aromatic copolyimide using Priamine 1075 (aliphatic) and m-tolidine (aromatic) as diamines. The branched bulky aliphatic units enlarge the free volume, effectively reducing the dipole moment density, while the aromatic diamine was introduced to prevent polymer chain relaxation under the operating conditions. We observed that there is an optimal composition that regulates the chain movement and density of dipole moments through the control of the polymer chain rigidity and nanostructure. Thus, by tuning the composition, we succeeded in achieving a low-dielectric copolyimide with a dielectric constant ( D k ) of 2.63 and dielectric loss ( D f ) of 0.0017 at 28 GHz. Combining molecular design and composition control, this study suggests a design factor for advanced copolymers for telecommunication applications with fast signal transport speed and minimum signal loss. The optimal molecular design for arresting chain motions achieves the lowest dielectric loss while minimizing the increase in the dielectric constant of copolyimide.

Influence of Hydrophobic Side-Chain Length in Amphiphilic Gradient Copoly(2-oxazoline)s on the Therapeutics Loading, Stability, Cellular Uptake and Pharmacokinetics of Nano-Formulation with Curcumin.

Due to the simple one-step preparation method and a promising application in biomedical research, amphiphilic gradient copoly(2-oxazoline)s are gaining more and more interest compared to their analogous block copolymers. In this work, the curcumin solubilization ability was tested for a series of amphiphilic gradient copoly(2-oxazoline)s with different lengths of hydrophobic side-chains, consisting of 2-ethyl-2-oxazoline as a hydrophilic monomer and 2-(4-alkyloxyphenyl)-2-oxazoline as a hydrophobic monomer. It is shown that the length of the hydrophobic side-chain in the copolymers plays a crucial role in the loading of curcumin onto the self-assembled nanoparticles. The kinetic stability of self-assembled nanoparticles studied using FRET shows a link between their integrity and cellular uptake in human glioblastoma cells. The present study demonstrates how minor changes in the molecular structure of gradient copoly(2-oxazoline)s can lead to significant differences in the loading, stability, cytotoxicity, cellular uptake, and pharmacokinetics of nano-formulations containing curcumin. The obtained results on the behavior of the complex of gradient copoly(2-oxazoline)s and curcumin may contribute to the development of effective next-generation polymeric nanostructures for biomedical applications.

Electrospinning Technique for Fabrication of Coaxial Nanofibers of Semiconductive Polymers.

In this work, the electrospinning technique is used to fabricate a polymer-polymer coaxial structure nanofiber from the p-type regioregular polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) and the n-type conjugated ladder polymer poly(benzimidazobenzophenanthroline) (BBL) of orthogonal solvents. Generally, the fabrication of polymeric coaxial nanostructures tends to be troublesome. Using the electrospinning technique, P3HT was successfully used as the core, and the BBL as the shell, thus conceptually forming a p-n junction that is cylindrical in form with diameters in a range from 280 nm to 2.8 µm. The UV-VIS of P3HT/PS blend solution showed no evidence of separation or precipitation, while the combined solutions of P3HT/PS and BBL were heterogeneous. TEM images show a well-formed coaxial structure that is normally not expected due to rapid reaction and solidification when mixed in vials in response to orthogonal solubility. For this reason, extruding it by using electrostatic forces promoted a quick elongation of the polymers while forming a concise interface. Single nanofiber electrical characterization demonstrated the conductivity of the coaxial surface of ~1.4 × 10-4 S/m. Furthermore, electrospinning has proven to be a viable method for the fabrication of pure semiconducting coaxial nanofibers that can lead to the desired fabrication of fiber-based electronic devices.

Antimicrobial Nanostructured Assemblies with Extremely Low Toxicity and Potent Activity to Eradicate Staphylococcus Aureus Biofilms.

Self-assembled cationic polymeric nanostructures have been receiving increasing attention for efficient antibacterial agents. In this work, a new type of antibacterial agents is developed by preparing pH-dependent nanostructured assemblies from cationic copolypeptoid poly(N-allylglycine)-b-poly(N-octylglycine) (PNAG-b-PNOG) modified with cysteamine hydrochloride ((PNAG-g-NH2 )-b-PNOG) driven by crystallization and hydrophobicity of the PNOG blocks. Due to the presence of confined domains arising from crystalline PNOG, persistent spheres and fiber-like assemblies are obtained from the same polymer upon a heating-cooling cycle. This allows for direct comparison of antimicrobial efficiency of nanostructured assemblies with various morphologies that are otherwise similar. Both nanostructured assemblies exhibit extremely low toxicity to human red blood cells, irrespective of the presence of the hydrophobic block. Enhanced antimicrobial performance of the fiber-like micelles compared to the spheres, which result in high selectivity of the fibers, is shown. Notably, the fiber-like micelles show great efficacy in inhibition of the Staphylococcus aureus (S. aureus) biofilm formations and eradication of the mature biofilms, superior to vancomycin. The micelles also show potent in vivo antimicrobial efficacy in a S. aureus infection mouse skin model. With a systematic study, it is demonstrated that both micelles kill the bacteria through a membrane disruption mechanism. These results imply great potential of polypeptoid assemblies as promising excellent candidates for antibacterial treatment and open up new possibilities for the preparation of a new generation of nanostructured antimicrobials.

Polyoxometalate-polymer nanocomposites with multiplex proton transport channels for high-performance proton exchange membranes

Multiplex ion channels play a critical role in life processes and are highly desired for advanced electrolytes due to the synergistic effect on ion transport. However, it is a challenge to integrate different types of proton transport channels in the same membrane system while keeping their intrinsic structural stability. Here, we report a facile strategy for the preparation of nanostructured polymer composite membranes with multiplex proton transport channels based on the supramolecular co-assembly of sulfonated poly(ether-ether-ketone) (SPEEK), poly(ether-ether-ketone)-grafted-poly(vinyl pyrrolidone) (PGP) and polyoxometalate H3PW12O40 (PW). The spherical ionic domains from SPEEK and the bicontinuous ionic domains from the electrostatically assembled PGP/PW components were fabricated in the membranes simultaneously, which co-construct the multiplex channels for proton conduction. The optimized membranes exhibit a high proton conductivity of ∼130 mS/cm and a high modulus of ∼4.3 GPa, which are ∼2.2 and ∼1.3 times higher than the pristine SPEEK, respectively. Furthermore, the direct methanol fuel cell performance based on these membranes is enhanced by 50.4% compared to SPEEK. This approach can provide a paradigm to design advanced polymer electrolyte membranes with highly efficient ion-conducting channels for energy applications.

Influence of the Poly(ethylene Glycol) Methyl Ether Methacrylates on the Selected Physicochemical Properties of Thermally Sensitive Polymeric Particles for Controlled Drug Delivery.

Thermosensitive copolymers P1-P5 of N-isopropylacrylamide (NIPA) and poly(ethylene glycol) methyl ether methacrylates (PEGMEMs) were synthesized via surfactant-free precipitation polymerization (SFPP) using ammonium persulfate (APS) at 70 °C. The polymerization course was evaluated by the conductivity. The hydrodynamic diameters and the polydispersity indexes (PDI) of P1-P5 in the 18-45 °C range, which were assessed via dynamic light scattering (DLS), were at 18° (nm): 26.07 ± 0.54 (PDI 0.65 ± 0.03), 68.00 ± 1.10 (PDI 0.56 ± 0,02), 45.12 ± 0.57 (PDI 0.51 ± 0.03), 62.78 ± 0.40 (PDI 0.53 ± 0.003), and 92.95 ± 1.56 (PDI 0.60 ± 0.04), respectively. The lower critical solution temperatures ranged from 31 to 33 °C. The electrophoretic mobilities estimated the zeta potential in the 18-45 °C range, and at 18 °C, they were (mV): -4.64 ± 1.30, -6.91 ± 2.67, -5.85 ± 3.17, -2.28 ± 0.30, and -3.60 ± 0.96 for P1-P5, respectively. The polymers were characterized by Attenuated Total Reflectance Fourier-Transform Infrared spectroscopy (ATR-FTIR), H nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA/DTA), Differential Scanning Calorimetry (DSC), and powder X-ray diffraction analysis (PXRD). Stable amorphous polymers were obtained. We conclude that the length of the co-monomer chain nonlinearly influences the properties of the obtained thermosensitive polymer nanostructures.

Effect of Polystyrene Synthesis Method on Water Sorption and Glass Transition.

Commodity PS is synthesized via free radical polymerization, whereas PS in block copolymers (BCPs) is typically synthesized via living anionic polymerization. The purpose of this work is to investigate how the synthesis method impacts important properties such as water sorption and glass transition temperature (Tg). Water sorption is important because the performance of nanostructured polymer membranes in various applications is known to be affected by environmental conditions such as humidity. Tg is important because it dictates processing conditions, both for commodity PS as well as BCPs such as thermoplastic elastomers. Water sorption in commercial PS was found to be 0.5 mgwater/gpolymer at the highest humidities investigated (about 80%), in agreement with literature. On the other hand, syndiotactic PS synthesized anionically at low temperature absorbed more water, up to 1.5 mgwater/gpolymer, due to higher free volume. The greatest impact on water sorption was due to addition of hydrophilic hydroxyl chain ends to atactic PS, which resulted in water sorption of up to 2.3 mgwater/gpolymer. In addition to measuring water sorption and dry Tg separately, the impact of relative humidity on PS Tg was examined. Combined differential scanning calorimetry and dynamic mechanical analysis show that on going from the dry state to high humidity, the Tg of PS decreases by 5 °C. Moreover, the tensile storage modulus of PS decreases from 1.58 GPa at 0% RH to 0.53 GPa at 40% RH. In addition to the practical relevance of this study, this report fills a gap in experimental literature by using a poor solvent system, PS/water, to examine plasticization in the pure polymer limit.