Crosslinker diacrylate

A variation of UV-NIL developed initially for semiconductor fabrication is known as SFIL and utilizes resist formulations based on UV-initiated free radical generation. The multicomponent resist for SFIL is comprised of an acrylate, a crosslinking diacrylate, a silicon-containing acrylate, and corresponding photoinitiator and surfactant. The resist is commonly... 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

Recently, Kloosterboer (W) accumulated a number of data on fast polymerization of diacrylates. He has also shown that the density of the system decreases with increasing crosslinking density. The initiated (kinetic) percolation model described the structure of the resulting system much better than any other model. 

In many applications densely crosslinked, glassy polymers are desired. Such polymers can be made by photopolymerization of suitable diacrylates. Important parameters are the rate of polymerization, the maximum extent of reaction and the... 

In this contribution we present results obtained with tetra-ethyleneglycol diacrylate (TEGDA). This compound was chosen since its polymer shows an easily discernible maximum in the mechanical losses as represented by tan 5 or loss modulus E" versus temperature when it is prepared as a thin film on a metallic substrate. When photopolymerized at room temperature it forms a densely crosslinked, glassy polymer, just as required in several applications. Isothermal vitrification implies that the ultimate conversion of the reactive double bonds is restricted by the diffusion-limited character of the polymerization in the final stage of the reaction. Therefore, the ultimate conversion depends strongly on the temperature of the reaction and so does the glass transition. 

Fig. 1 Enzymatic routes (a-c) of telechelic diacrylates by enzymatic ROP for subsequent crosslinking. X denotes the polymerizable (meth)acrylate group...

He et al. (2) prepared a hydrolyzably crosslinked biodegradable network consisting of poly(propylene fumarate) crosslinked with the diacrylate derivative of poly(propylene fumarate), (I). 

To demonstrate the UV crosslinkability of the polymers formed having pendant acyloxyimino groups, copolymers of bisphenol diacrylate and 1,6 hexanediol diacrylate were prepared by thermal methods with 5% (by weight) of pyrene oxime acrylate and phenanthrene oxime acrylate, both of which have considerable absorption in the region of 320-360 nm. The polymerization was stopped before the gel point and the prepolymer solutions were then irradiated with light from a monochromator at the maximum of... 

FI3. Fox, T. G., and J. C. H. Hwa Crosslinked polymers. III. Efficiency of intermolecular crosslinking before gelation in methyl methacrylate-diacrylate and dimethacrylate copolymers. Vortrag vor der Polymer Division of the 131st National Am. Chem. Soc. Meeting, Miami 1957. 

Acrylic Crosslinkers. Butanediol diacrylate (IV) (BDDA) is a popular crosslinker used in the preparation of many polymers used for inks, paints, and plastics. Low-levels of impurities can adversely affect product properties. As previously discussed, K+IDS provides a powerful qualitative technique, but yields poor quantitative data when analyzing volatile chemicals. BDDA is amenable to analysis by GC, unfortunately any higher-molecular-weight adducts exceed the volatility range amenable to GC. Moreover, BDDA is not chromophoric thereby HPLC characterization is also difficult. 

Figure 2. K+IDS mass spectrum of butanediol diacrylate crosslinker (IV). Scan rate 100 - 1000 Da/sec, average of five scans. Consult reference 12 for specific details.

Reaction-induced phase separation is certainly also the reason for which an inhomogeneous structure is observed for photocured polyurethane acrylate networks based on polypropylene oxide (Barbeau et al., 1999). TEM analysis demonstrates the presence of inhomogeneities on the length scale of 10-200 nm, mostly constituted by clusters of small hard units (the diacrylated diisocyanate) connected by polyacrylate chains. In addition, a suborganization of the reacted diisocyanate hard segments inside the polyurethane acrylate matrix is revealed by SAXS measurements. Post-reaction increases the crosslink density inside the hard domains. The bimodal shape of the dynamic mechanical relaxation spectra corroborates the presence of a two-phase structure. 

Figure 10.3 Mean molecular mass between chemical crosslinks and trapped chain entanglements Mc+e in a cured mixture of a poly(ethylene glycol) diacrylate (PEGDA) and 2-ethylhexyl acrylate (EHA) as a function of the EHA content [52]. Mc+e values were determined from (1/T2s)max and the plateau modulus (see Figure 10.2). A substantial difference in Mc+e value, as determined by these two methods at low crosslink density, is caused by the effect of network defects which decrease volume average network density determined by DMA (see Section 10.3). The molecular mass of PEGDA (Mn = 700 g/mol) is indicated by an arrow. The molecular mass of network chains in cured PEGDA is about three times smaller than that of the initial monomer. The molecular origin of this difference is discussed in Section 10.3...

The base rubber is produced by polymerization of an acrylate in emulsion. A crosslinker can be employed, e.g. a diol diacrylate such as butanediol diacry late, divinylbenzene allyl(meth)acrylate, dioldiallylcarbonate, acrylic esters of... 

The main disadvantage of the use of -y-irradiation is that the drug has to be incorporated at the primary emulsification step and is therefore exposed to the 7-irradiation. To overcome this difficulty Law et al (44) have synthesised a series of acryolyl derivatives of certain poloxamer surfactants. Bredimas et al (45) have shown that it is possible to stabilise an unstable o/w emulsion by polymerisation of diacrylate surfactant molecules in surface crosslinking reactions. We have confirmed this (44) and have succeeded in stabilizing w/o/w emulsions, the primary emulsion comprising isopropyl myristate with 5% Span 80 and 0.9% of the diacryloyl derivative of Pluronic L44 in the aqueous phase (0 =... 

The following protocols (6-10) describe the synthesis of some cholesterol-based acrylates and their photopolymerization in an aligned cholesteric phase. The protocols utilize a modification of a system previously described by Shannon. 5 6 ip ie absence of a diacrylate comonomer, the cholesteric phase produced initially on copolymerization is not stable and reverts to a smectic phase on a single cycle of heating and cooling. In the presence of the diacrylate the first-formed phase is stable. This is one example of how crosslinking can stabilise the liquid crystal phase in liquid crystalline elastomers, others include, the so-called, polymer-stabilized liquid crystals and those described in the later protocols. 

Different labile crosslinkers have different rates of bond cleavage at different temperatures. The temperature required and the mechanism of bond dissociation depend on the chemical structure of the crosslinker. For example, when the labile crosslinker is a diacrylate ester, hydrolysis of the ester linkage becomes the most likely mechanism of de-crosslinking. Proper selection of crosslinker can give particles with different activation temperature. The product... 

One of the aspects of polymer-supported reactions (see Section 4) is the ability to separate reactive centres from each other. The extent to which a benzoin condensation reaction occurs on a crosslinked polymer was examined [45]. The starting material, a polymeric benzaldehyde, was prepared by incorporation of vinyl benzaldehyde into a resin using either divinylbenzene or tetraethyleneglycol diacrylate as a crosslinker. The product was examined using CP/MAS. The spectra showed two important peaks at 86.2, 126.0 and 166.0 ppm. These were attributed to the a-hydroxy carbon, the proton-ated aromatic carbons and the carbonyl carbon of the a-hydroxy ketone. This demonstrated that in the polymer the benzoin condensation reaction had occurred to a significant extent. 

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