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Increasing demand and high rates of non-attendance (DNA) lengthen waiting lists for psychiatric services, a topic of significant public and political interest. NHS Lothian data between 2009/10 and 2018/19 averaged a DNA rate of 19% for new patient appointments. Our aim was to analyse the waiting list and DNA rate for patients referred for a routine Consultant-led General Adult Psychiatry outpatient clinic appointment (OPCA) within the North-West Edinburgh Community Mental Health Team. The goal was to identify lost clinical time and areas for service development.
We collected data of all patients on the waiting list for a routine OPCA, excluding ‘soon’ or ‘urgent’ appointments and those on the separate Neurodevelopmental Disorder waiting list.
We collected data of all OPCA attendances between 1st of January 2020 and 1st of January 2023.
In line with Royal College of Psychiatrists guidance, we allocated 30 minutes for a return patient and 60 minutes for a new patient to determine lost clinical time due to DNAs.
Data were collected from NHS Lothian Analytical Services and anonymised in line with NHS Information Governance Policy.
221 patients were on the waiting list for an appointment. 52% of patients were female (n = 115). The longest wait was 10 months.
Between the 1st of January 2020 and the 1st of January 2023, 1961 new patient appointments were booked. 263 were cancelled prior to the appointment. Of the appointments remaining, 30% were DNAs (n = 505), resulting in 505 lost clinical hours, an average of 168 hours/year.
9172 return patient appointments were booked. 1189 were cancelled in advance. 22% were DNAs (n = 1812), resulting in 906 hours of lost clinical hours, an average of 302 hours/year.
DNAs have a direct impact on service provision. Were our service to reduce our DNAs to the Lothian average for General Adult Psychiatry new patient OPCA, we would save on average 61 clinical hours/year.
We will disseminate this information to the NHS Lothian Digital Experience Mental Health Team to support the introduction of a text reminder service, before involving the NHS Lothian Quality Improvement team to explore the impact of this intervention on DNAs.
Furthermore, being placed on a waiting list can be an uncertain time for patients. We will create a waiting list pack for patients, including information of local supports and emergency contacts. We will pilot this in our sector before disseminating to other teams in Lothian.
A low temperature amorphous zinc indium oxide (ZIO) thin film transistor (TFT) backplane technology for high information content flexible organic light emitting diode (OLED) displays has been developed. We have fabricated 4.1-in. diagonal OLED backplanes on the Flexible Display Center’s six-inch wafer-scale pilot line using ZIO as the active layer. The ZIO based TFTs exhibited an effective saturation mobility of 18.6 cm2/V-s and a threshold voltage shift of 2.2 Volts or less under positive and negative gate bias DC stress for 10000 seconds. We report on the critical steps in the evolution of the backplane process: the qualification of the low temperature (200°C) ZIO process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication of white organic light emitting diode (OLED) displays.
Principal challenges to direct fabrication of high performance a-Si:H transistor arrays on flexible substrates include automated handling through bonding-debonding processes, substrate-compatible low temperature fabrication processes, management of dimensional instability of plastic substrates, and planarization and management of CTE mismatch for stainless steel foils. In collaboration with our industrial and academic partners, we have developed viable solutions to address these challenges, as described in this paper.
Aerogels were structurally modified using chemical vapor deposition (CVD) of cyanoacrylate monomers to afford polycyanoacrylate-aerogel nanocomposites. Silica aerogels are low density, high surface area materials whose applications are limited by their fragility. Cyanoacrylate CVD allowed us to deposit a film of organic polymer throughout fragile porous monoliths within hours. Our experiments have shown that polymerization of the cyanoacrylate monomers was initiated by the adsorbed water on the surface of the silica permitting the nanocomposites structures to be formed with little or no sample preparation. We found that the strength of the polycyanoacrylate-aerogel nanocomposites increased thirty two-fold over the untreated aerogels with only a three-fold increase in density and an eight-fold decrease in surface area. Along with the improvement in mechanical properties, the aerogels became less hydrophilic than un-modified aerogels. Polycyanoacrylate-coated aerogels were placed directly into water and did not suffer catastrophic fragmentation as observed with un-modified silica aerogels.
The introduction of organic substituents into sol-gel materials can often result in networks that collapse during drying to afford non-porous xerogels. This can prove useful if non-porous coatings or membranes are the ultimate objectives. Collapse of porosity is also manifested in bridged polysilsesquioxanes with flexible bridging groups. Alkylene-bridged polysilsesquioxanes are hybrid xerogels whose organic bridging group is an integral constituent of the network polymer that can be systematically varied to probe the influence of its length on the xerogels' porosity and morphology. Our previous studies have shown that hexylene-bridged polysilsesquioxane xerogels prepared from 1, 6-bis(triethoxysilyl)hexane under acidic conditions are nonporous while the pentylene-bridged polysilsesquioxanes prepared under the same conditions are porous. We also discovered that the more reactive 1, 6-bis(trimethoxysilyl)hexane monomer could polymerize under acidic conditions to afford porous xerogels. Here, we have extended our study of bis(trimethoxysilyl)alkanes to include the heptylene (C7), octylene (C8), nonylene(C9) and decylene (C10) bridges so as to ascertain at what bridging group length the porosity collapses. The morphology of the resulting xerogels was characterized by nitrogen sorption porosimetry and electron microscopy. Solid state NMR was used to structurally characterize the materials.
Aging of silica gels before drying is known to result in significant changes in xerogel morphology, porosity and properties. In this study, the influence of aging gels on the porosity and morphology of alkylene-bridged polysilsesquioxane xerogels was examined. Gels of hexylene-, heptylene, octylene, nonylene, and decylene-bridged polysilsesquioxanes were prepared by the sol-gel polymerization of the respective bis(trimethoxysilyl)alkane monomers under acidic or basic conditions in methanol and in tetrahydrofuran. The gels were aged 3, 7, 14, 28, 35, 42, 49, and 56 days before drying to afford xerogels. The xerogels were characterized by nitrogen sorption porosimetry. Xerogels prepared in THF were non-porous. Those prepared and aged under basic conditions in methanol or tetrahydrofuran exhibited coarsening of porosity with aging time. With the exception of the hexylene-bridged gels, those prepared and aged in acidic methanol showed little change with aging. The surface area of the hexylene-bridged xerogels nearly tripled with aging times of up to several weeks, then decreased, for the gels aged for more than two weeks, to around 100 meters squared per gram.
High molecular weight polysilsesquioxanes with carboxylate functionalities were prepared by sol-gel polymerization of organotrialkoxysilanes bearing tert-butyl ester groups. Trialkoxysilyl-containing monomers of the type (RO)3Si(CH2)3C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH3CHCH2C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.
This issue of MRS Bulletin focuses on the preparation and application of hybrid organic–inorganic materials, which are broadly defined as synthetic materials with organic and inorganic components. Hybrid organic–inorganic materials are of two kinds: homogeneous systems derived from monomers or miscible organic and inorganic components, and heterogeneous and phase-separated systems with domains ranging from angstroms to micrometers in size.
Hydrolysis and condensation of trialkoxysilanes, HSi(OMe)3 and HSi(OEt)3, has been used to prepare polyhydridosilsesquioxaes for dielectric applications. In this study we examined the ability of trimethoxysilane (TMS) and triethoxysilane (TES) to undergo sol-gel polymerization to afford gels. Sol-gel polymerization experiments were conducted under acidic (HCl), basic (NaOH), and neutral conditions in methanol or ethanol. Gels prepared with basic catalysts were exothermic with the evolution of hydrogen gas. Gel times are compared with silica gels prepared from tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS). Gels were worked up under aqueous conditions to afford xerogels. Surface area analyses by nitrogen sorption porosimetery revealed that the materials were mostly mesoporous materials with surface areas in the hundreds of square meters per gram. Solid state 29Si CP MAS NMR was used to determine the amount of hydrido group remaining in the xerogels. Gels prepared under acidic conditions were essentially polysilsesquioxanes with very little loss of hydride functionalities. In gels prepared under basic conditions the hydride groups were completely gone leaving silica gels. Gels prepared with neutral water lost approximately 66% of the hydride groups.
Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid orgainc-inorganic materials . These materials have shown promise as precursors for encapsulation and microelectronics applications (Figure 1). The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.
Organopolysilsesquioxanes have recently gained much interest as materials for low-K dielectrics , ceramic precursors  and photoresists . Typical sol-gel synthesis of polysilsesquioxanes involves the hydrolysis of organotricholorosilanes and/or organotrialkoxysilanes in the presence of acid or base catalysts and organic solvents. However, under sol-gel conditions most organotrialkoxysilanes do not afford silsesquioxane gels. This limits the range of organic functionalities that can be introduced into these hybrid organicinorganic materials.
Polymerization of organotrialkoxysilanes is a convenient method for introducing organic functionality into hybrid organic-inorganic materials. However, not much is known about the effects of the organic substituent on the porosity of the resulting xerogels. In this study, we prepared a series of polysilsesquioxane xerogels from organotrialkoxysilanes, RSi(OR′)3, with different organic groups (R = H, Me, Et, dodecyl, hexadecyl, octadecyl, vinyl, chloromethyl, cyanoethyl). Polymerizations of the monomers were carried out under a variety of conditions, varying monomer concentration, type of catalyst, and alkoxide substituent. The effect of the organic substituent on the sol-gel process was often dramatic. In many cases, gels were formed only at very high monomer concentration and/or with only one type of catalyst. All of the gels were processed as xerogels and characterized by scanning electron microscopy and nitrogen sorption porosimetry to evaluate their pore structure.
In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, solubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300–350°C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.
Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. We have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits us to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solvent is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which we have successfully demonstrated.
Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane 1 and 1,4-bis(triethoxysilyl)butane 2 were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed with the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possiblity of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.
While the sol-gel polymerizations of tetraalkoxy- and organotrialkoxysilanes have been extensively studied, there have been few reports of similar investigations with the analogous tetraalkoxygermanium and organotrialkoxygermanium compounds. Germanium alkoxides have received less attention due, in part to their higher cost, but also their greater reactivity towards hydrolysis and condensation reactions. Germanium oxide materials are potentially interesting because the Ge-O-Ge linkage is labile (compared with the siloxane bond in silica gels and polysilsesquioxanes) opening up the possibility of further chemical modification of the polymeric architecture. This may permit hydrolytic reorganization of germanium oxide networks under relatively mild conditions. In this paper, we will present the results of our investigations of the solgel polymerizations of tetraethoxygermanium 1, tetraisopropoxygermanium 2, and methyltriethoxy-germanium 3 to afford network materials as both xerogels and aerogels.
The retro Diels-Alder reaction was used to modify porosity in hydrocarbon-bridged polysilsesquioxane gels. Microporous polysilsesquioxanes incorporating a thermally labile Diels-Alder adduct as the hydrocarbon bridging group were prepared by sol-gel polymerization of trans-2, 3-bis(triethoxysilyl)norbornene. Upon heating the 2, 3-norbornenylene-bridged polymers at temperatures above 250°C, the norbornenylene-bridging group underwent a retro Diels-Alder reaction losing cyclopentadiene and leaving behind a ethenylene-bridged polysilsesquioxane. Less than theoretical quantities of cyclopentadiene were volatilized indicating that some of the diene was either reacting with the silanol and olefinic rich material or undergoing oligomerization. Both scanning electron microscopy and nitrogen sorption porosimetry revealed net coarsening of pores (and reduction of surface area) in the materials with thermolysis.
We investigate the porosity of a series of xerogels prepared from arylene-bridged silsesquioxane xerogels as a function of organic bridging group, condensation catalyst and post-synthesis plasma treatment to remove the organic functionalities. We conclude that porosity is controlled by polymer-solvent phase separation in the solution with no evidence of organic-inorganic phase separation. As the polymer grows and crosslinks, it becomes increasingly incompatible with the solvent and eventually microphase separates. The domain structure is controlled by a balance of network elasticity and non-bonding polymer-solvent interactions. The bridging organic groups serve to ameliorate polymer-solvent incompatibility. As a result, when the polymer does eventually phase separate, the rather tightly crosslinked network limits domain size to tens of angstroms, substantially smaller than that observed in xerogels obtained from purely inorganic precursors where incompatibility drives phase separation earlier in the gelation sequence.
Arylene- and alkylene-bridged polysilsesquioxanes were prepared by sol-gel
processing of bis(triethoxysilyl)-arylene monomers 1-4, and alkylene
monomers 5-9. The arylene polysilsesquioxanes were porous materials with
surface areas as high as 830 m2/g (BET). Treatment with an
inductively coupled oxygen plasma resulted in the near quantitative removal
of the arylene bridging groups and a coarsening of the pore structure. Solid
state 29Si NMR was used to confirm the conversion of the
sesquioxane silicons (T) to silica (Q). The alkylene-bridged
polysilsesquioxanes were non-porous. Oxygen plasma treatment afforded silica
gels with mesoporosity. The porosity in the silica gels appears to arise
entirely from the oxidation of the alkylene spacers.