Polyhedral Oligomeric Silsesquioxane Nanoparticles Research Articles

Toward the Highly Ordered Lamellar Hybrid Membrane for Molecular Sieving by One-Pot Self-Assembly of Hybrid Hyperbranched Polymer

Ordered lamellar hybrid membranes are of great interest, due to their application as functional materials, including molecular sieving, biosensors, optical devices, and drug, as well as gene delive...

Chain Dimension and Dynamics of Polymers in Well-Defined Non-sticky Nanocomposites of Molecular Nanoparticle Polyhedral Oligomeric Silsesquioxane/Poly(butylene oxide)

The chain dimension and dynamics of type-A polymer, poly(1, 2-butylene oxide) (PBO), in the nanocomposites comprising polyhedral oligomeric silsesquioxane (POSS) nanoparticles have been investigated in broad frequency and temperature windows by utilizing broadband dielectric spectroscopy and rheology. Non-crystalline and dielectric “invisible” molecular nanoparticle POSS was specially designed to ensure its miscibility with the PBO matrix, which was verified by quantitative estimation of solubility parameters and subsequent X-ray scattering experiments. Dispersions of POSS in the PBO matrix up to 10 vol % have been investigated. Dielectric experiments revealed a negligible change of the dielectric relaxation strength of the normal mode and thus the statistical chain dimension of PBO, regardless of the POSS loadings and the polymer chain lengths spanning from the unentangled to the entangled region. The introduction of nanoparticles is found to influence both the chain and segment dynamics when the molecular weight of the polymer is relatively low. However, by renormalized with the segmental relaxation, the dielectric chain relaxation shows identical characteristic relaxation time with that of the neat polymer, independent of the volume fractions of POSS, which is consistent with the terminal relaxation time determined in the rheology experiments. The slowing down of segmental relaxation has been attributed to the influence of nanoparticles on the chain ends associated with excess free volume. The possible confinement, solvent, and filler effects in this type of a non-sticky nanocomposite model system have been further discussed.

A novel mineralized high strength hydrogel for enhancing cell adhesion and promoting skull bone regeneration in situ

Bone defect therapy based on advanced biocomposite hydrogel scaffolds provide a promising strategy in bone tissue engineering. Inducing bone regeneration that meets the biomechanical, bioactivity and osteoconductivity criteria of bone tissue engineering is highly appealing but challenging. Here, we designed a mineralized, high-strength and tough nanocomposite hydrogel by in situ deposition of calcium phosphate hydroxide salt nanohydroxyapatite (HAP) after photopolymerization of gelatin methacryloyl (GelMA), quaternized chitosan (QCS) and functional polyhedral oligomeric silsesquioxane (POSS), in which the POSS nanoparticles served as a physical-chemical crosslinker to reinforce the hydrogel network structure and improved mineralized capacity by silicon in POSS nanoparticle bonding to calcium ions. The fabricated nanocomposite hydrogels have excellent mechanical properties (tensile strength of 328.6 ± 14.3 kPa and compressive strength of 1.71 ± 0.24 MPa) and high cytocompatibility, significantly facilitated cell adhesion and upregulated osteodifferentiation. After treatment of a rat skull defect model for 12 weeks, the scaffold of the biomineralized hydrogel remarkably promoted new bone formation and accelerated bone regeneration in situ, suggesting its used as a promising substitute in bone tissue engineering.

The Role of POSS Functionality on Induced Deviation of Nano and Micromechanical Properties of UV Curable Urethane Acrylate Nanocomposite Coatings

The inorganic-organic hybrid coatings based on UV curable urethane acrylate contained two types of polyhedral oligomeric silsesquioxane (POSS) were prepared. The hydroxyl functionalized POSS nanoparticles, pristine POSS, and the one modified by acrylic acid utilized to study the effect of nanoparticle content and its functionality on ultimate mechanical properties of the hybrid coatings. The nanomechanical properties and scratch resistance of nanocomposite coatings were evaluated with nanoindentation and nanoscratch techniques, respectively. Consequently, the results compared with previously obtained DMTA data. The results revealed that by embedding acrylic acid modified POSS, the surface hardness and elastic modulus improved. Further increasing acrylic acid modified POSS content to 5%, the surface elastic modulus and hardness improved to 37% and 35%, respectively, relative to neat coating and also the enhanced scratch resistance was observed. Furthermore, the discrepancy between the surface elastic modulus and bulk elastic modulus was rationalized and the contributed parameters that led to this deviation such as pile-up area, holding time and hydrostatic stress was investigated. The results showed that apart from the inefficiency of Oliver and Pharr method to precisely evaluate the nanomechanical properties of hybrid coatings, the targeted placement of POSS nanoparticle is responsible for this disparity between surface mechanical properties and its bulk values.

Functionalized polar Octa(γ-chloropropyl) polyhedral oligomeric silsesquioxane assisted polyimide nanofiber composite membrane with excellent ionic conductivity and wetting mechanical strength towards enhanced lithium-ion battery

Based on the urgent demand of excellent wetting mechanical strength electrospun nanofiber separators and some doping compounds which are beneficial to enhance electrochemical performance for Li-ion cell, in this study, a natty nanofiber composite membrane based on heat-resistant polyimide (PI) matrix via introducing polar Octa (γ-chloropropyl) polyhedral oligomeric silsesquioxane (OCP-POSS) nanoparticles for the first time is resoundingly prepared by electrospinning technology. The hybrid PI/OCP-POSS separator (HOPS separator) with 3.5 wt% OCP-POSS nanoparticles presents significant improvement in wetting mechanical strength (11.8 MPa), eminent electrolyte retention rate (1025%) together with a tendency of gelation phase and still exerts laudable high thermal stability. Meanwhile, the battery with the HOPS separator exhibits preferable electrochemical stability window (5.2 V) and exceedingly excellent ionic conductivity (2.8 × 10−3 S cm−1). The most extraordinary is that the capacity retention reaches up to 81.45% after 100 cycles at 0.2 C and 91.96% in C-rates test, while the pristine PI separator merely achieves to 56.03% and 75.90%, respectively. In addition, the modified separator possesses more stable cycling properties than PP separator (Celgard 2400) at 1 C and 2 C rate, respectively, which all fully signifies that the heat-resistant HOPS separator has great application prospects in high-performance and advanced-safety lithium-ion battery.

Main Chain-Type Block Copolymers through Atom Transfer Radical Polymerization from Double-Decker-Shaped Polyhedral Oligomeric Silsesquioxane Hybrids.

In this study, we synthesized two main chain–type block copolymers featuring hydrogen bond donor and acceptor segments through atom transfer radical polymerization (ATRP) using a bifunctionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the initiator. Hydrosilylation of vinylbenzyl chloride at the two corners of a double-decker silsesquioxane (DDSQ) provided the bifunctionalized benzyl chloride initiator VBC-DDSQ-VBC, which we applied as a platform to prepare a main chain–type polystyrene homopolymer (PS-DDSQ-PS), the diblock copolymer poly(styrene–b–4-vinylpyridine) (P4VP-b-PS-DDSQ-PS-b-P4VP), and the diblock copolymer poly(styrene–b–tert-butoxystyrene) (PtBuOS-b-PS-DDSQ-PS-b-PtBuOS) through sequential ATRP. Selective hydrolysis of the tert-butoxyl units of PtBuOS-b-PS-DDSQ-PS-b-PtBuOS yielded the strongly hydrogen bonding diblock copolymer poly (styrene-b-vinylphenol) (PVPh-b-PS-DDSQ-PS-b-PVPh). We used Fourier transfer infrared spectroscopy, nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, mass-analyzed laser desorption ionization mass spectrometry, and transmission electron microscopy to investigate the chemical structures, thermal behavior, and self-assembled nanostructures formed by these main chain–type block copolymers based on DDSQ.

Peptide 18-4/chlorin e6-conjugated polyhedral oligomeric silsesquioxane nanoparticles for targeted photodynamic therapy of breast cancer

Chlorin e6 (Ce6), with its high phototoxic potential, has wide applications in photodynamic therapy (PDT) for many human diseases. However, poor cancer cell localization of Ce6 has limited its direct application for PDT. Here, we developed cancer-targeting peptide p 18-4/chlorin e6 (Ce6)-conjugated polyhedral oligomeric silsesquioxane (PPC) nanoparticles for improving the targeting ability of Ce6 to breast cancer cells, thereby enhancing PDT efficacy. The synthesized PPC nanoparticles exhibited a spherical shape with an average diameter of 127.2 ± 11.3 nm in aqueous solution. Compared with free Ce6, the immobilization of p 18-4 enhanced the in vitro cellular uptake and targeting ability of PPC nanoparticles in breast cancer cell line MDA-MB-231. In addition, the intracellular uptake of PPC nanoparticles in MDA-MB-231 cells was dramatically increased compared with other cancer cells, indicating an obvious targeting ability of PPC nanoparticles on breast cancer cells. Upon light irradiation, PPC nanoparticles revealed significantly improved phototoxicity to MDA-MB-231 cells, mainly due to apoptotic cell death. In vivo PDT study suggested that PPC nanoparticles exhibited increased retention in tumor tissues and effectively inhibited the growth of MDA-MB-231 tumors in a target-specific manner. Overall, these results indicate that PPC nanoparticles are highly effective PDT agents for breast cancer therapy.

Near-field scattering enhancement of perylene based aggregates for random lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N’-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide (DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

Effect of Alkyl Chain Length in POSS Nanocage on Non-Isothermal Crystallization Behavior of PCL/Amino-POSS Nanocomposites.

The study of the non-isothermal crystallization behavior of polymers is of great importance due to the effect of degree of crystallinity and crystallization process on the polymer properties. The effect of aminopropylisobutyl polyhedral oligomeric silsesquioxane (APIBPOSS) and aminopropylisooctyl polyhedral oligomeric silsesquioxane (APIOPOSS) on poly(ε-caprolactone) (PCL) crystallization is studied by differential scanning calorimetry (DSC) under non-isothermal conditions and polarized optical microscopy (POM). The crystallization kinetics is analyzed using the Avrami and Mo models, and effective activation energies are evaluated by the Friedman isoconversional method. The results show that the compatibility between polyhedral oligomeric silsesquioxanes (POSS) and PCL and POSS loading affect the crystallization process. A higher crystallization temperature, a narrower size distribution of crystallite, and a faster crystallization rate are obtained in the presence of all the studied contents of APIBPOSS and at lower contents of APIOPOSS. At APIOPOSS contents higher than 2 wt %, the crystallization temperature is lowered, the size distribution of crystallite is broadened, and the crystallization process is retarded. The presence of POSS leads to an increase in the number of nucleation sites, and a reduction in the size of the crystallite and the overall degree of crystallinity, as a result of the confinement of PCL chains caused by POSS nanoparticles.

Using Methacryl-Polyhedral Oligomeric Silsesquioxane as the Thermal Stabilizer and Plasticizer in Poly(vinyl chloride) Nanocomposites.

In this study, we investigated the influence of methacryl-functionalized polyhedral oligomeric silsesquioxane (MA-POSS) nanoparticles as a plasticizer and thermal stabilizer for a poly(vinyl chloride) (PVC) homopolymer and for a poly(vinyl chloride)/dissononyl cyclohexane-1,2-dicarboxylate (PVC/DINCH) binary blend system. The PVC and the PVC/DINCH blend both became flexible, with decreases in their glass transition temperatures and increases in their thermal decomposition temperatures, upon an increase in MA-POSS content, the result of hydrogen bonding between the C=O groups of MA-POSS and the H–CCl units of the PVC, as determined using infrared spectroscopy. Furthermore, the first thermal decomposition temperature of the pure PVC, due to the emission of HCl, increased from 290 to 306 °C, that is, the MA-POSS nanoparticles had a retarding effect on the decomposition of the PVC matrix. In tensile tests, all the PVC/DINCH/MA-POSS ternary blends were transparent and displayed flexibility, but their modulus and tensile strength both decreased, while their elongation properties increased, upon an increase in MA-POSS concentration, both before and after thermal annealing. In contrast, the elongation decreased, but the modulus and tensile strength increased, after thermal annealing at 100 °C for 7 days.

In-situ growth of Ag on mussel-inspired polydopamine@poly(M-POSS) hybrid nanoparticles and their catalytic activity

Polyhedral oligomeric silsesquioxane (POSS) nanoparticles have gain much attention due to their organic and inorganic hybrid structure that combine with metal nanoparticles to improve their functional properties for utilize in potential application areas. In this study, we first time present a green route for in-situ growth of silver on the surface of POSS based support particles by using mussel inspired polydopamine (PDA) coating. The POSS based nanocomposite support were synthesized by free radical mechanism in one-step emulsion polymerization of methacryl(M)-POSS monomer. Smooth spherical shape in size range of 200 nm–400 nm poly(M-POSS) hybrid latex particles were covered by the functional amine and catechol groups of PDA. Silver layer were growth on PDA@poly(M-POSS) nanocomposite template. The novel multi-functional Ag@PDA@poly(M-POSS) nanocomposite particles were fully characterized by SEM, EDAX, XRD and FTIR analysis. The catalytic activity of the particles was checked by pseudo-first order kinetic reaction of nitrophenol compound, which is highly toxic for environment. The catalytic reaction performance was discussed by varying the catalyst amount and concentration of 4-nitrophenol. Compare to similar catalysts, results showed that Ag@PDA@poly(M-POSS) nanocomposite particles exhibited excellent catalytic activity for the rapid degradation of 4-NP.

Enhanced compatibility of starch with poly(lactic acid) and poly(ɛ-caprolactone) by incorporation of POSS nanoparticles: Study on thermal properties

In this work, we explore the ability of polyhedral oligomeric silsesquioxane (POSS) nanoparticles to increase the compatibility of hydrophilic starch with hydrophobic poly(lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL). Morphological analysis demonstrated that lower contents of POSS (0.5 and 1 wt%) enhances the compatibility of the system. However, higher inclusion of POSS results in the formation of aggregates and thus a lower level of compatibility. Transmission electron microscopy revealed that PCL acts as an intermediate between PLA and starch, and that POSS is primarily localized within the PLA and PCL phases. Based on differential scanning calorimetry, PLA's crystallinity increases from 22.9% to 31.6% upon adding a very low content of POSS (0.5 wt%). However, the PCL's crystallinity is slightly hampered due to formation of these PLA crystallites. In contrast with the crystallization behavior and based on the thermal degradation kinetics, we found the composite's thermal stability is greatly increased when moderate to high contents (3 and 5 wt%) of POSS are utilized. Dynamic mechanical analysis results also confirmed good POSS dispersion within the matrix, especially at lower contents. In conclusion, POSS serves as an efficient compatibilizer for PLA/starch/PCL systems with improved thermal properties.

An assessment on the effect of trifluoropropyl-POSS and blend composition on morphological, thermal and thermomechanical properties of PLA/TPU

The influence of blending ratio and trifluoropropyl polyhedral oligomeric silsesquioxane (POSS) on microstructure, melt and cold crystallization behavior, thermomechanical and thermal stability of melt-blended polylactic acid/thermoplastic polyurethane (PLA/TPU) blends was investigated using various techniques. Morphological observations (TEM and EDX) showed that POSS nanoparticles have a good dispersion state throughout the matrix and localize in both phases and also at the blend interface. POSS nanoparticles hindered the melt crystallization of PLA while enhancing the degree of cold crystallinity of PLA. In addition, the dispersed TPU droplets in PLA matrix induced a nucleation effect on melt crystallization of PLA, especially at low contents. On the contrary, the cold crystallization temperature of PLA shifted to a higher temperature in the presence of TPU phase, but the degree of crystallinity improved in the case of heating with a low rate. Although the addition of TPU to PLA resulted in a decrement in onset degradation temperature, the samples degraded in wider ranges than neat PLA. The onset degradation temperature of samples in inert ambient was declined by the addition of POSS due to its low thermal stability. These nanoparticles slightly enhanced the thermal stability of PLA-rich samples in air ambient but had no sensible effect on TPU-rich samples. The storage modulus values of the PLA/TPU blends gradually decreased with increasing TPU content. In addition, incorporation of POSS nanoparticles, generally, increased the values of storage modulus but reduced the glass transition temperature, proving the lubrication effect of POSS nanoparticles.

Armor polyamide reverse osmosis membrane with POSS ‘armors’ through two-step interfacial polymerization for high anti-chlorine and anti-bacteria performance

Improvement of anti-chlorine and anti-bacterial properties of membranes has been a major challenge in desalinating process. In this paper, zero-dimension cage-like structure polyhedral oligomeric silsesquioxane (POSS) was in situ armored on the surface of polyamide (PA) membrane and acted as ‘armors’ to prevent active chlorine corrosion and bacterial fouling. PA/POSS hybrid membranes could be easily achieved through a simple two-step interfacial polymerization. Anti-chlorine and anti-bacterial properties of PA/POSS hybrid membranes significantly improved during desalination by tuning the content of POSS ‘armors’. Salt rejection reached approximately 98% after immersing PA/POSS hybrid membranes in the active chlorine solution for 24 h, which showed excellent anti-chlorine property. In addition, the anti-bacterial property of PA reverse osmosis (RO) membranes extremely enhanced after armoring with POSS nanoparticles. This finding demonstrated that the structure and chemical inert nature of POSS enabled PA/POSS membranes to block active chlorine and bacteria. PA/POSS membranes provided a promising approach to improve membrane desalination.

Effect of silsesquioxane addition on the protective performance of fluoropolymer coatings for bronze surfaces

Two types of innovative coatings based on fluoroethylene/vinylether alternating copolymers are investigated as protective systems for bronze works-of-art. The influence of a polyhedral oligomeric silsesquioxane (POSS), i.e. open-cube trisilanol-heptaisooctyl-POSS, on the surface, mechanical, optical and electrochemical properties of coatings is examined. It is found that the isooctyl groups in the organic shell of POSS cause an increase in the hydrophobicity of the surface. On the other hand, nanoindentation tests show that the reduced modulus, hardness and plasticity index decrease with the addition of POSS, while abrasion resistance is slightly improved. Haze of coatings increases when POSS nanoparticles are present. More importantly, a beneficial effect of POSS addition on the protective efficiency against corrosion is assessed by exposure of coatings to acidic vapours and electrochemical treatments. In this regard, potentiodynamic polarisation clearly shows that the protective efficiency is systematically larger for coatings comprising POSS. The ex situ IR reflection-absorption spectroelectrochemistry shows that cuprous oxide can eventually form at the coating|bronze interface, which is identified through the spectroelectrochemistry of unprotected bronze.

Effects of an Organic-Inorganic Hybrid Containing Allyl Benzoxazine and POSS on Thermal Properties and Flame Retardancy of Epoxy Resin.

A novel organic-inorganic hybrid containing allyl benzoxazine and polyhedral oligomeric silsesquioxane (POSS) was synthesized by the thiol-ene (click) reaction. The benzoxazine (BOZ)-containing POSS (SPOSS-BOZ) copolymerized with benzoxazine/epoxy resin was used to prepare composites of SPOSS-PBZ-E nanocomposites(NPs). The polymerization behavior was monitored by FTIR and non-isothermal differential scanning calorimetry (DSC), which showed that the composites had completely cured with multiple polymerization mechanisms according to the oxazine ring-opening and epoxy resin (EP) polymerization. The thermal properties of the organic–inorganic polybenzoxazine (PBZ) nanocomposites were analyzed by DSC and thermogravimetric analysis (TGA). Furthermore, the X-ray diffraction analysis and the scanning electron microscopy (SEM) micrographs of the SPOSS-PBZ-E nanocomposites indicated that SPOSS was chemically incorporated into the hybrid nanocomposites in the size range of 80–200 nm. The flame retardancy of the benzoxazine epoxy resin composites was investigated by limiting oxygen index (LOI), UL 94 vertical burn test, and cone calorimeter tests. When the amount of SPOSS reached 10% or more, the vertical burning rating of the curing system arrived at V-1, and when the SPOSS-BOZ content reached 20 wt %, the thermal stability and flame retardancy of the material were both improved. Moreover, in the cone calorimeter testing, the addition of SPOSS-BOZ hindered the decomposition of the composites and led to a reduction in the peak heat release rate (pHRR), the average heat release rate (aHRR), and the total heat release (THR) values by about 20%, 25%, and 25%, respectively. The morphologies of the chars were also studied by SEM and energy dispersive X-ray spectroscopy (EDX), and the flame-retardant mechanism of POSS was mainly a condensed-phase flame retardant. The ceramic layer was formed by the enrichment of silicon on the char surface. When there are enough POSS nanoparticles, it can effectively protect the combustion of internal polymers.

Understanding of Leading-Edge Protection Performance Using Nano-Silicates for Modification

Leading edge erosion caused by raindrop impact is a key problem that needs to be overcome in the wind energy sector. Solutions up to date have not proved suitable, failing prematurely in their lifecycle at a cost to the wind industry. Failure mechanisms for rain erosion are not well understood, particularly the elastic and viscous polymer properties at the resulting high strain rates (106 - 109 Hz) of raindrop impacts. The effect of the inclusion of glycidyl polyhedral oligomeric silsesquioxane nanoparticles into a commercial polyurethane coating system was studied using nanoindentation and dynamic mechanical thermal analysis (DMTA). Results show that the inclusion of POSS improves damping, providing an alternative mechanism for energy dissipation without variation of Tg and minimal loss of stiffness. This presents a way of modifying current coating systems through the incorporation of POSS. Nanoindentation obtained previously unreported properties of the coating system (hardness, modulus and short-term recovery) and highlighted a correlation between loading rate and a reduction of short-term recovery. Nanoindentation was difficult for the modified leading-edge protection (LEP) samples as two phases were formed resulting in large standard deviations. DMTA results show modification of the LEP increases damping at lower temperature ranges introducing an additional mechanism of dissipating energy. Additionally, sweep data show an increase in elasticity at higher frequencies on the modified samples.

Synthesis and evaluation of the effect of structural parameters on recovery rate of shape memory polyurethane-POSS nanocomposites

Recovery rate and recovery stress are important factors that limit the use of polyurethanes, especially in the medical field. In this study, Polyhedral Oligomeric Silsesquioxane nanoparticles as chain extender have been bonded to polyurethane chains using a new synthesis method. Fourier-transform infrared spectroscopy technique to confirm synthesis reactions, Differential Scanning Calorimetry for evaluating the effect of Polyhedral Oligomeric Silsesquioxane (POSS) particles on the crystallinity of soft segments, Dynamic Mechanical Thermal Analysis for investigating mechanical properties, and Scanning Electron Microscope and X-ray diffraction have been used to evaluate the dispersion of Nanoparticles, respectively. It is observed that using Polyhedral Oligomeric Silsesquioxane solely, acts as a chain extender which does not show phase separation in synthesized nanocomposites. Using both the Polyhedral Oligomeric Silsesquioxane and 1,4-Butanediol chain extender in polyurethane synthesis reaction caused greater phase separation rather than solely 1,4-Butanediol. Finally, adding the nanoparticles caused improvement in recovery rate as well as shape recovery in the synthesized nanocomposites.

Versatile Construction of Single-Tailed Giant Surfactants with Hydrophobic Poly(ε-caprolactone) Tail and Hydrophilic POSS Head.

Giant surfactants refer to a new kind of amphiphile by incorporating functional molecular nanoparticles with polymer tails. As a size-amplified counterpart of small-molecule surfactants, they serve to bridge the gap between small-molecule surfactants and amphiphilic block copolymers. This work reports the design and synthesis of single-tailed giant surfactants carrying a hydrophobic poly(ε-caprolactone) (PCL) as the tail and a hydrophilic cage-like polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the head. The modular synthetic strategy features an efficient “growing-from” and “click-modification” approach. Starting from a monohydroxyl and heptavinyl substituted POSS (VPOSS-OH), a PCL chain with controlled molecular weight and narrow polydispersity was first grown by the ring-opening polymerization (ROP) of ε-CL under the catalysis of stannous octoate, leading to a PCL chain end-capped with heptavinyl substituted POSS (VPOSS-PCL). To endow the POSS head with adjustable polarity and functionality, three kinds of hydrophilic groups, including hydroxyl groups, carboxylic acids, and amine groups, were installed to the periphery of POSS molecule by a high-efficiency thiol-ene “click” reaction. The compounds were fully characterized by NMR, gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, and TGA analysis. In addition, the preliminary self-assembly study of these giant surfactants was also investigated by TEM and dynamic laser light scattering (DLS), which indicated that they can form spherical nanoparticles with different diameters in aqueous solution. This work affords a straightforward and versatile way for synthesizing single-tailed giant surfactants with diverse head surface functionalities.

Sustained release of plasmid DNA from PLLA/POSS nanofibers for angiogenic therapy

Angiogenesis plays a critical role to provide a desired microenvironment during tissue repair and regeneration. Gene-activated scaffold is increasingly showing potential in tissue engineering and regenerative medicine. Herein, functional polyhedral oligomeric silsesquioxane (POSS) nanoparticles, known for the organic-inorganic structure and biocompatibility, were incorporated into poly(l-lactic acid) (PLLA) matrix and processed by electrospinning into nanofibers as a delivery vehicle of plasmid DNA encoding angiopoietin-1 (pAng). The introduction of functional POSS nanoparticles increased the strength and toughness of the matrix simultaneously, and formed the porous fiber structure. PAng released from the nanofibrous scaffold showed sustained delivery over 35 days and maintained high transfection efficiency. A full-thickness skin wound model was used to evaluate the pAng delivery efficacy and angiogenesis capability of the plasmid DNA-based polymeric scaffold in vivo. The results indicated that the pAng loaded PLLA/POSS scaffold effectively promoted angiogenesis and dermal wound healing.