Highly cross-linked UV-cured siloxane copolymer networks as icephobic coatings

Preventing ice growth on infrastructure, vehicles, and appliances remains a significant engineering challenge. Damage caused by ice growth on these installations can be expensive to repair, and their failure can be dangerous. Materials such as cross-linked polymer networks make effective anti-ice coatings and can prevent ice growth: reducing the cost of infrastructure repairs and limiting downtime. A link between cross-link density and ice adhesion has been demonstrated, such that lower cross-link density materials tend toward lower ice adhesion. Here we describe a method of lowering cross-link density by incorporating the covalently bound comonomers methyl methacrylate, lauryl methacrylate, and styrene into UV-cured PDMS-based polymer networks. Cross-link density, hardness, surface roughness, and ice adhesion on these materials are tested, showing the influence of comonomer proportions on their properties. Durability is found to increase with the addition of 5, 10, and 25 wt% comonomer, with little to no effect on ice adhesion until 25 wt%, where increases in ice adhesion are observed. Coatings show promisingly low ice adhesion of ~50 kPa, maintaining this low adhesion for up to 50 deicing cycles.     

嵌段共聚物核交联胶束的制备与载药性能研究

在DMAP的催化和DIPC的作用下,丙烯酸的双键被引入聚乙二醇-聚己内酯嵌段共聚物的疏水链段上,制备胶束过程中使用过硫酸铵催化位于胶束内核部分的双键交联,得到的核交联胶束。在包载甲氨喋呤释放过程中,核交联胶束的累积释放率明显比非核交联胶束的小,具有良好的缓释效果。     

Influence of the composition on the glass transition temperature of polyurethane and polyurethane acrylate networks

Linear polyurethane, linear segmented polyurethane, polyurethane networks, and polyurethane acrylate networks of various composition were synthesized. The variation of T_g with the type of macrodiol, its length, and the chemical composition of the polymer were studied in relation with the percentage of soft segments, the molar mass between crosslinks, and the concentration of urethane bonds. In this work, the networks were considered as composed of chain segments of various composition between point-like crosslinks. The chemical heterogeneities of the networks were not taken into account. For polyurethanes, it was shown that T_g values are essentially controlled by the amount of urethane bonds. For polyurethane acrylates, the T_g values are dependent on the amount of urethane bonds but also on the presence of crosslinks whose number is varying with the excess of diisocyanate of the first step three times faster for PUA compared with PU. No clear relation was observed between T_g and the molar mass between point-like crosslinks. Another approach considering the network heterogeneities is indispensable and will be used in a following work. © 1996 John Wiley & Sons, Inc.     

丙烯酸十六酯与丙烯酸共聚物凝胶的合成及其性能

合成了丙烯酸十六酯(HA)与丙烯酸(AA)的共聚物凝胶，研究了共聚组成对共聚物凝胶性能的影响。结果表明：经二甲亚砜(DMSO)平衡溶胀后的凝胶，在HA与AA的物质的量比为1：1时，具有较高的规整性。溶剂的极性对聚合物凝胶的规整性有较大的影响。DSC及X射线衍射表明共聚物凝胶具有液晶性能。     

Polyurethane/polyethyl acrylate interpenetrating polymer networks

The thermal decomposition kinetics of polyurethane/polyethyl acrylate interpenetrating polymer networks (PU/PEA IPN) were studied by means of thermogravimetry and derivative thermogravimetry (TG-DTG), and compared with those of polyurethane (PU) and polyethyl acrylate (PEA). The decomposition temperature (T _i) of PU/PEA IPN was found to be higher thanT _i of PEA, but lower thanT _i of PU. Thermal decomposition kinetic parameters,n andE, estimated using Coats-Redfern method, are found for PU/PEA IPN, PU and PEA to be 1.6, 1.9 and 1.1, and 196.6, 258.6 and 139.2 kJ mol^–1, respectively. The results show that PU/PEA IPN is neither a simple mixture of PU and PEA nor a copolymer of them. The mechanism of thermal decomposition of PU/PEA IPN is different from those of PU and PEA. The special network in PU/PEA IPN effectually protects weak bonds in the molecular chain of PU and PEA.We express our thanks to Dr. Yaxiong Xie and Zhiyuong Ren for their help in this work,     

Effect of monoacrylate type in UV curable PU acrylate based bicontinuous polymer/liquid crystal networks

Polymer network liquid crystals (PNLC) have been prepared from ultraviolet-curable polyurethane acrylate (PUA) and a nematic liquid crystal mixture (BL002). Effects of monoacrylate type on film morphology, temperature-dependent off-state transmittance, and electro-optic performance of the film have been studied. Among three types of monoacrylates incorporated (EHA(2-ethyl hexyl acrylate), MMA (methylmethacryalte), NVP (N-vinylpyrrolidone)), EHA-based PUAs gave the greatest polymer–LC phase separation, lowest threshold (V₁₀), and operating (V₉₀) voltages, and the effect was more pronounced in monoacrylate/triacrylate systems than in monoacrylate/diacrylate systems. Contact angle measurement offers a clue to the observed morphology and electro-optic behavior. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1393–1399, 1998     

Long‐range order in physical networks of gel‐forming triblock copolymer solutions

Structural studies on physical gels, based on a triblock copolymer and a solvent selective for its midblocks, are presented. Gel formation in such systems arises due to interconnected microdomains that form the junctions in a three‐dimensional network. Small angle X‐ray scattering studies revealed that the physical networks show either short‐range order, described by an effective hard sphere model, or long‐range order, where junctions are arranged on a cubic lattice. The emerging morphology depends on the thermal conditions during preparation of such systems, which essentially reflects a competition among microdomain ordering and formation of the physical network. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1833–1840, 1999     

Photopolymerization and toughening performance in polypropylene of hyperbranched polyurethane acrylate

A novel UV-curable hyperbranched polyurethane acrylate (HUA) was synthesized and found to polymerize rapidly in the presence of 5 wt.% benzophenone in N₂ under UV exposure. The photopolymerization kinetics of HUA was studied by differential photocalorimetry (DPC). Its toughening effect for polypropylene (PP) was investigated by tensile and impact tests of the UV irradiated PP/HUA blends. The morphological structures and thermal behavior were determined by polarized optical microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The obtained results demonstrate that (1) the maximum photopolymerization rate increases with raising temperature up to 140 °C, whereas decreases at above 150 °C. The activation energy of 19 kJ mol⁻¹ for the photopolymerization was obtained at below 140 °C from the Arrhenius plot, while it is negative at above 150 °C. (2) The incorporation of 5 wt.% HUA greatly improved the notched impact strength of PP matrix with a slight improvement in the tensile strength and without obvious decline in breaking elongation. These results correlate well with SEM observation. (3) During the UV irradiation of PP/HUA blends, PP can be crosslinked/grafted with the cured HUA particles, resulting in the increase of the impact strength of PP matrix. (4) The cured HUA particles in the PP/HUA blends act as heterogeneous nucleation agent for PP, which results in the decrease of spherulite size and less perfection of PP crystals.     

Bulk and microscopic properties of copolymer networks in mixed aqueous solvents

Amphiphilic films and hydrogels have been prepared from ethanol/water solutions containing a hydrocarbon-grafted water-soluble cellulose ether. These materials are characterized by dispersed hydrophobic microdomains which form spontaneously in the solvent due to the inherent incompatibility of the side chains with water. At low applied shear stress, the microdomains behave as temporary linkages of finite lifetimes, imparting viscoelastic properties to the networks. The molecular weight between microdomains was found to be independent of the volume fraction of polymer in the gel, and the number of linkages per backbone ranges from 22.8 ± 1.3 to 26.2 ± 1.5 over the frequency range 30–50 rad/s. The behavior of the solutions and gels was characterized using fluorescence and dynamic rheological measurements. It was demonstrated that the microdomains are capable of sequestering water-insoluble solutes. © 1992 John Wiley & Sons, Inc.     

Influence of different copolymer sequences in low band gap polymers on their performance in organic solar cells

The chemical design of a polymer can be tailored by a random or a block sequence of the comonomers in order to influence the properties of the final material. In this work, two sequences, PCPDTBT and F8BT (F8), were polymerized to form a block or a random copolymer. Differences between the various polymers were examined by exploring the surface topography and charge carrier mobility. A distinct surface texture and a higher charge carrier mobility was found for the block copolymer with respect to the other materials. Solar cells were prepared with polymer:PC₇₁BM blend active layers and the best performance of up to 2% was found for the block copolymer, which was a direct result of the fill factor. Overall, the sequences of different copolymers for solar cell applications were varied and a positive impact on efficiency was found when the block copolymer structure was utilized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Tunable Amphiphilic Poly(Ether-Anhydride) Gel Nanoparticles for the Delivery of Hydrophobic Drugs

Summary: Biodegradable amphiphilic poly(ether-anhydride) gel nanoparticles (GNPs) with a hydrophobic crosslinked core and a hydrophilic PEG shell have been prepared from amphiphilic photo-crosslinkable ether-anhydride macromers via microemulsion photo-polymerization. The properties of the GNPs, such as degradability, size and drug-loading capacity, were investigated by tailoring the length of PEG chains in macromers from 400 to 4000 and by the addition of a hydrophobic photo-crosslinkable monomer: stearic monoacrylic anhydride (MSA). TEM showed that the GNPs were spherical in shape with a core-shell structure when MSA was added. The GNPs were used as the carriers to enhance the solubility of hydrophobic drugs. Indomethacin (IND) as a model drug was entrapped in the hydrophobic crosslinked core by an in situ embedding method. Results showed that IND maintained chemically intact during the formulation process, and its dissolution rate were improved compared to those of the pure IND. The GNPs prepared from PEG macromer (molecular weight: 4000) with the addition of MSA exhibited the zero-order release behavior, which is potentially useful to control the release of hydrophobic drugs.     

Practical implementation of order parameter calculation for directed assembly of block copolymer thin films

A computational procedure is presented to quantify the order achieved in assembled block copolymer films when no disruptive defects are present (i.e., dislocations or disclinations). Both simulated and real systems were used to show that sub‐nm variation in the domain position, as well as the corresponding reciprocal lattice vectors, can reduce the accuracy in the quantification of the order of the system. The computational procedure in this work was based on fitting to the measured spatial location of the domain centroids, and incorporated a tolerance factor to account for domain position variation. The procedure was used to analyze the translational and orientational order parameters of block copolymer films assembled on a chemical pattern as well as their corresponding autocorrelation functions. The procedure was applied to a patterned substrate during three stages of a template forming process: an e‐beamed patterned photoresist, the domains of a block copolymer directed to assemble on this pattern, and the underlying structure after lift‐off. Use of the procedure demonstrated that the order of the block copolymer film could be retained in subsequent processing of the underlying template. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Semi-interpenetrating polymer networks synthesis by photocrosslinking of acrylic monomers in a polymer matrix

Semi-interpenetrating polymer networks have been obtained by UV-radiation curing of acrylate monomers dispersed in a polymer matrix, using an arylketone as photoinitiator. The polymerization kinetics was studied quantitatively by infrared spectroscopy for the various polymers examined: polyurethane, poly(vinyl chloride), poly(methyl methacrylate). The fastest reaction occurs in PVC films, where UV-curing develops extensively within a fraction of a second, leading to an insoluble and highly resistant material. The functionality of the acrylic monomer has a strong influence on the formulation reactivity, as well as on the mechanical and chemical properties of the final product. In PMMA, the polymerization was shown to continue to proceed efficiently for a few seconds after the UV exposure, even in the presence of air, due to both the high concentration of initiating radicals generated by the intense irradiation and the slow termination processes in solid media. © 1993 John Wiley & Sons, Inc.     

Synthesis of enantiopure 1,2-diamine attached to cross-linked polystyrene and its application to an insoluble catalyst for asymmetric hydrogenation

A novel enantiopure 1,2-diamine (5) having two phenolic hydroxy groups was attached into chloromethylated polystyrene through benzyl ether linkage, which was used as a chiral ligand of the catalyst in asymmetric hydrogenation of acetophenone.     

Graft copolymer of polymethyl methacrylate-g-polycarbonate urethane and the fully gelled grafted networks

We have synthesized and characterized the graft copolymer of polymethyl methacrylate (PMMA)-graft-polycarbonate urethane (PCU) (designated PMMA-g-PCU) and the fully gelled mutually crosslinked network composed of both PMMA and PCU (designated as PMMA-PCU-N). Unlike the previously synthesized one phase PCU/PMMA simultaneous interpenetrating polymer networks (IPN's), both of these new materials exhibited two distinct T_g's (from DSC and DMA studies) at all compositions which we have studied. The two-phase nature of the graft and network polymer was confirmed by TEM with domain sizes smaller than those found in the blends of the linear PCU and PMMA chains. In comparison with the corresponding IPN's, the PMMA-g-PCU and the PMMA-PCU-N were thermally less stable and had a lower ultimate strength. © 1992 John Wiley & Sons, Inc.     

New Polymeric Adsorbents Functionalized with Aminobenzoic Groups for the Removal of Residual Antibiotics

In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chloromethylated styrene–divinylbenzene (DVB) copolymers with different cross-linking degrees functionalized with the following aminobenzoic groups: styrene—6.7% DVB (PAB1), styrene—10% DVB (PAB2), and styrene—15% DVB (PAB3). The new polymeric products, PAB1, PAB2, and PAB3, were characterized by FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis, respectively. The evolution of the functionalization reaction was followed by FTIR spectroscopy, which revealed a decrease in the intensity of the γCH₂Cl band at 1260 cm⁻¹, and, simultaneously, the appearance of C=O carboxylic bands from 1685–1695 cm⁻¹ and at 1748 cm⁻¹. The thermal stability increased with the increase in the cross-linking degree. The data obtained from the EDX analysis of the novel cross-linked copolymers confirmed the functionalization with aminobenzoic groups through the presence and content of nitrogen, as follows: PAB1: N% = 0.47; PAB2: N% = 0.85; and PAB3: N% = 1.30. The adsorption performances of the novel polymeric adsorbents, PAB1, PAB2, and PAB3, were tested in the adsorption of three antibiotics, tetracycline, sulfamethoxazole, and amoxicillin, from aqueous solutions, by using extensive kinetic, equilibrium, and thermodynamic studies. The best adsorption capacity was demonstrated by the tetracycline. Amoxicillin adsorption was also attempted, but it did not show positive results.     

Synthesis of polyethylene oxide graft polysilylenes and networks based on poly(di‐n‐pentylsilylene/n‐pentyloct‐7‐enyl) copolymers

Poly(dipentylsilylene) copolymers containing n‐pentyl‐n‐oct‐7‐enylsilane units were prepared by reductive coupling of the corresponding dichlorosilanes. Linear high molecular weight and some crosslinked polymer were obtained. The soluble products exhibited optical and thermal properties like poly(dipentylsilylene). Differential scanning calorimetry was used to investigate crystallization and to monitor thermal crosslinking. Vinyl functionalized side chains were hydrosilylated with dipentylsilane and dimethylchlorosilane and crosslinked via the side chains. Hydrosilylation with di‐n‐pentyl(trimethylsiloxypropyl)silane led to a partial hydroxy functionalization of the polysilylene and enabled anionic PEO grafting of the poly(dipentylsilylene). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2306–2318, 2000     

层状复合氢氧化物的制备改性及其对热塑性硫化胶的阻燃作用

用氩载氨气泡膜限域共沉淀反应合成了层状复合氢氧化物(LDH)及其硬脂酸改性样品,与热塑性硫化胶Santoprene熔炼制成LDH/Santoprene复合材料,在EDS、XRD、IR和N2吸解表征的基础上,对LDH-Santoprene复合物的机械性能及燃烧性能进行了测试评价.结果表明所用合成方法能够实现小尺寸LDH微晶的快速合成与表面改性,微晶粒度及表面性能明显改观;改性样品对Santoprene有更好的复合效果和明显的阻燃作用.     

Structure and flow behavior of crosslinked ethyl acrylate–methacrylic acid copolymer dispersion particles

 Changes in viscosity, pH and static light scattering behavior on alkali addition of model dispersions of statistical copolymers of ethyl acrylate with 15 and 50 wt% of methacrylic acid prepared by semicontinuous emuslion copolymerization and crosslinked with various amount of N,N′-methylenebisacrylamide were investigated. It was found that about 1% of crosslinking agent was sufficient to prevent unpredictable disintegration of dispersion particles and gauranteed reproducible flow behavior of alkalinized dispersions. The viscosity of alkalinized dispersions of crosslinked particles at low concentration is controlled by the effective hydrodynamic volume of swelled particles which decreases with the crosslinking degree of copolymer. On the other hand, at higher particle concentration close to critical concentration at which the space is filled up by swelled particles the influence of particle interaction prevails and due to lower deformability of crosslinked particles viscosity increases with a crosslinking degree. In comparison with similar dispersions prepared without a crosslinking agent these results indicated much uniform structure of dispersion particles and suppression of influence of random crosslinking due to chain transfer reactions. The study shows that dispersions of crosslinked copolymers of this type could be considered as thickners of latex binders with stable and reproducible thickening properties. Received: 23 February 1998 Accepted: 11 June 1998